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The 1990 season’s official transaction log: 640 trades, signings and releases involving major-league clubs, listed newest first.
| Date | Type | Player | From | To | Details |
|---|---|---|---|---|---|
| Dec 30, 1990 | Trade | Unnamed | Los Angeles Dodgers | Texas Rangers | $ |
| Dec 30, 1990 | Trade | Steve Allen | Texas Rangers | Los Angeles Dodgers | Trade |
| Dec 30, 1990 | Trade | Dave Lynch | Texas Rangers | Los Angeles Dodgers | Trade |
| Dec 30, 1990 | Trade | Jim Poole | Los Angeles Dodgers | Texas Rangers | Trade |
| Dec 23, 1990 | Trade | Ivan Calderon | Chicago White Sox | Montreal Expos | Trade |
| Dec 23, 1990 | Trade | Barry Jones | Chicago White Sox | Montreal Expos | Trade |
| Dec 23, 1990 | Trade | Tim Raines | Montreal Expos | Chicago White Sox | Trade |
| Dec 23, 1990 | Trade | Jeff Carter | Montreal Expos | Chicago White Sox | Trade |
| Dec 22, 1990 | Signed as free agent | Joe Redfield | — | Pittsburgh Pirates | Free agent signing |
| Dec 21, 1990 | Signed as free agent | Larry Andersen | — | San Diego Padres | Free agent signing |
| Dec 21, 1990 | Signed as free agent | Steve Fireovid | — | Pittsburgh Pirates | Free agent signing |
| Dec 21, 1990 | Signed as free agent | Chuck Jackson | — | Seattle Mariners | Free agent signing |
| Dec 21, 1990 | Signed as free agent | Alonzo Powell | — | Seattle Mariners | Free agent signing |
| Dec 20, 1990 | Signed as free agent | Mike Campbell | — | Milwaukee Brewers | Free agent signing |
| Dec 20, 1990 | Released | Ozzie Canseco | Oakland Athletics | — | Release |
| Dec 20, 1990 | Signed as free agent | Charlie Leibrandt | — | Atlanta Braves | Free agent signing |
| Dec 20, 1990 | Released | Johnny Ray | California Angels | — | Release |
| Dec 20, 1990 | Signed as free agent | Danny Sheaffer | — | Minnesota Twins | Free agent signing |
| Dec 20, 1990 | Trade | Darren Holmes | Los Angeles Dodgers | Milwaukee Brewers | Trade |
| Dec 20, 1990 | Trade | Bert Heffernan | Milwaukee Brewers | Los Angeles Dodgers | Trade |
| Dec 19, 1990 | Signed as free agent | Tom Brunansky | — | Boston Red Sox | Free agent signing |
| Dec 19, 1990 | Signed as free agent | Mike Dalton | — | Detroit Tigers | Free agent signing |
| Dec 19, 1990 | Signed as free agent | Danny Darwin | — | Boston Red Sox | Free agent signing |
| Dec 19, 1990 | Signed as free agent | Mickey Hatcher | — | Los Angeles Dodgers | Free agent signing |
| Dec 19, 1990 | Signed as free agent | Donnie Hill | — | California Angels | Free agent signing |
| Dec 19, 1990 | Signed as free agent | Bill Krueger | — | Seattle Mariners | Free agent signing |
| Dec 19, 1990 | Signed as free agent | Dan Petry | — | Detroit Tigers | Free agent signing |
| Dec 19, 1990 | Signed as free agent | Scott Sanderson | — | Oakland Athletics | Free agent signing |
| Dec 19, 1990 | Signed as free agent | Don Slaught | — | Pittsburgh Pirates | Free agent signing |
| Dec 19, 1990 | Signed as free agent | Mickey Tettleton | — | Baltimore Orioles | Free agent signing |
| Dec 19, 1990 | Signed as free agent | Fernando Valenzuela | — | Los Angeles Dodgers | Free agent signing |
| Dec 18, 1990 | Signed as free agent | Rafael Belliard | — | Atlanta Braves | Free agent signing |
| Dec 18, 1990 | Signed as free agent | Randy Bush | — | Minnesota Twins | Free agent signing |
| Dec 18, 1990 | Released | Bill Long | Chicago Cubs | — | Release |
| Dec 18, 1990 | Trade | Jimmy Williams | Minnesota Twins | San Francisco Giants | Trade |
| Dec 17, 1990 | Signed as free agent | Danny Cox | — | Philadelphia Phillies | Free agent signing |
| Dec 17, 1990 | Signed as free agent | Ken Griffey | — | Seattle Mariners | Free agent signing |
| Dec 17, 1990 | Released | Randy Kramer | Chicago Cubs | — | Release |
| Dec 17, 1990 | Signed as free agent | Dave Smith | — | Chicago Cubs | Free agent signing |
| Dec 17, 1990 | Trade | Pedro Pena | Oakland Athletics | San Francisco Giants | Trade |
| Dec 16, 1990 | Signed as free agent | Juan Samuel | — | Los Angeles Dodgers | Free agent signing |
| Dec 15, 1990 | Signed as free agent | Jack Clark | — | Boston Red Sox | Free agent signing |
| Dec 15, 1990 | Released | Ray Searage | Los Angeles Dodgers | — | Release |
| Dec 15, 1990 | Signed as free agent | Bob Welch | — | Oakland Athletics | Free agent signing |
| Dec 15, 1990 | Trade | Hubie Brooks | Los Angeles Dodgers | New York Mets | Trade |
| Dec 15, 1990 | Trade | Bob Ojeda | New York Mets | Los Angeles Dodgers | Trade |
| Dec 15, 1990 | Trade | Greg Hansell | New York Mets | Los Angeles Dodgers | Trade |
| Dec 15, 1990 | Trade | Steve Hendricks | San Diego Padres | Boston Red Sox | Trade |
| Dec 15, 1990 | Trade | Brad Hoyer | San Diego Padres | Boston Red Sox | Trade |
| Dec 15, 1990 | Trade | Wes Gardner | Boston Red Sox | San Diego Padres | Trade |
| Dec 14, 1990 | Signed as free agent | Juan Agosto | — | St. Louis Cardinals | Free agent signing |
| Dec 14, 1990 | Released | Marty Barrett | Boston Red Sox | — | Release |
| Dec 14, 1990 | Signed as free agent | Brett Butler | — | Los Angeles Dodgers | Free agent signing |
| Dec 14, 1990 | Signed as free agent | Mario Diaz | — | Texas Rangers | Free agent signing |
| Dec 14, 1990 | Signed as free agent | Ted Power | — | Cincinnati Reds | Free agent signing |
| Dec 14, 1990 | Trade | Jose Vizcaino | Los Angeles Dodgers | Chicago Cubs | Trade |
| Dec 14, 1990 | Trade | Greg Smith | Chicago Cubs | Los Angeles Dodgers | Trade |
| Dec 14, 1990 | Trade | Paul Kilgus | Toronto Blue Jays | Baltimore Orioles | Trade |
| Dec 14, 1990 | Trade | Mickey Weston | Baltimore Orioles | Toronto Blue Jays | Trade |
| Dec 13, 1990 | Released | Luis Lopez | Los Angeles Dodgers | — | Release |
| Dec 13, 1990 | Released | Mark McLemore | Cleveland Indians | — | Release |
| Dec 13, 1990 | Signed as free agent | Gerald Perry | — | St. Louis Cardinals | Free agent signing |
| Dec 13, 1990 | Signed as free agent | Terry Puhl | — | New York Mets | Free agent signing |
| Dec 13, 1990 | Signed as free agent | Max Venable | — | California Angels | Free agent signing |
| Dec 12, 1990 | Signed as free agent | Floyd Bannister | — | California Angels | Free agent signing |
| Dec 12, 1990 | Signed as free agent | Todd Frohwirth | — | Baltimore Orioles | Free agent signing |
| Dec 12, 1990 | Signed as free agent | Charlie Hough | — | Chicago White Sox | Free agent signing |
| Dec 12, 1990 | Signed as free agent | Carl Willis | — | Minnesota Twins | Free agent signing |
| Dec 12, 1990 | Trade | Mark Parent | San Diego Padres | Texas Rangers | Trade |
| Dec 12, 1990 | Trade | Scott Coolbaugh | Texas Rangers | San Diego Padres | Trade |
| Dec 11, 1990 | Released | Tim Birtsas | Cincinnati Reds | — | Release |
| Dec 11, 1990 | Signed as free agent | Dave Henderson | — | Oakland Athletics | Free agent signing |
| Dec 10, 1990 | Signed | Carlos Almanzar | — | Toronto Blue Jays | Amateur free agent signing |
| Dec 10, 1990 | Signed | Edwin Hurtado | — | Toronto Blue Jays | Amateur free agent signing |
| Dec 10, 1990 | Signed as free agent | Gary Redus | — | Pittsburgh Pirates | Free agent signing |
| Dec 10, 1990 | Signed as free agent | Eric Show | — | Oakland Athletics | Free agent signing |
| Dec 10, 1990 | Signed | Dilson Torres | — | Toronto Blue Jays | Amateur free agent signing |
| Dec 10, 1990 | Trade | Scott Taylor | Seattle Mariners | Atlanta Braves | Trade |
| Dec 10, 1990 | Trade | Dennis Hood | Atlanta Braves | Seattle Mariners | Trade |
| Dec 9, 1990 | Signed as free agent | Jim Walewander | — | New York Yankees | Free agent signing |
| Dec 8, 1990 | Signed as free agent | Andy McGaffigan | — | Kansas City Royals | Free agent signing |
| Dec 7, 1990 | Signed as free agent | Fred Manrique | — | California Angels | Free agent signing |
| Dec 6, 1990 | Signed as free agent | George Bell | — | Chicago Cubs | Free agent signing |
| Dec 6, 1990 | Signed as free agent | Steve Crawford | — | Kansas City Royals | Free agent signing |
| Dec 6, 1990 | Signed as free agent | Dwight Evans | — | Baltimore Orioles | Free agent signing |
| Dec 6, 1990 | Released | Tony Fossas | Milwaukee Brewers | — | Release |
| Dec 6, 1990 | Released | Gus Polidor | Milwaukee Brewers | — | Release |
| Dec 6, 1990 | Signed as free agent | Zane Smith | — | Pittsburgh Pirates | Free agent signing |
| Dec 6, 1990 | Signed as free agent | Ron Tingley | — | California Angels | Free agent signing |
| Dec 5, 1990 | Signed as free agent | Tony Bernazard | — | Detroit Tigers | Free agent signing |
| Dec 5, 1990 | Signed as free agent | Sid Bream | — | Atlanta Braves | Free agent signing |
| Dec 5, 1990 | Signed as free agent | Vince Coleman | — | New York Mets | Free agent signing |
| Dec 5, 1990 | Signed as free agent | Bill Doran | — | Cincinnati Reds | Free agent signing |
| Dec 5, 1990 | Signed as free agent | Teddy Higuera | — | Milwaukee Brewers | Free agent signing |
| Dec 5, 1990 | Released | Mike Schwabe | Detroit Tigers | — | Release |
| Dec 5, 1990 | Signed as free agent | Franklin Stubbs | — | Milwaukee Brewers | Free agent signing |
| Dec 5, 1990 | Signed as free agent | Pat Tabler | — | Toronto Blue Jays | Free agent signing |
| Dec 5, 1990 | Trade | Johnny Ard | Minnesota Twins | San Francisco Giants | Trade |
| Dec 5, 1990 | Trade | Steve Bedrosian | San Francisco Giants | Minnesota Twins | Trade |
| Dec 5, 1990 | Trade | Joe Carter | San Diego Padres | Toronto Blue Jays | Trade |
| Dec 5, 1990 | Trade | Roberto Alomar | San Diego Padres | Toronto Blue Jays | Trade |
| Dec 5, 1990 | Trade | Fred McGriff | Toronto Blue Jays | San Diego Padres | Trade |
| Dec 5, 1990 | Trade | Tony Fernandez | Toronto Blue Jays | San Diego Padres | Trade |
| Dec 4, 1990 | Signed as free agent | Ravelo Manzanillo | — | Toronto Blue Jays | Free agent signing |
| Dec 4, 1990 | Signed as free agent | Rance Mulliniks | — | Toronto Blue Jays | Free agent signing |
| Dec 4, 1990 | Signed as free agent | Ed Nunez | — | Milwaukee Brewers | Free agent signing |
| Dec 4, 1990 | Signed as free agent | Dave Righetti | — | San Francisco Giants | Free agent signing |
| Dec 4, 1990 | Released | Billy Jo Robidoux | Boston Red Sox | — | Release |
| Dec 4, 1990 | Signed as free agent | Dan Schatzeder | — | Kansas City Royals | Free agent signing |
| Dec 4, 1990 | Signed as free agent | Ed Vosberg | — | California Angels | Free agent signing |
| Dec 4, 1990 | Signed as free agent | Matt Young | — | Boston Red Sox | Free agent signing |
| Dec 4, 1990 | Trade | Ken Rivers | Toronto Blue Jays | California Angels | Trade |
| Dec 4, 1990 | Trade | Dave Martinez | California Angels | Baltimore Orioles | Trade |
| Dec 4, 1990 | Trade | Mike Hook | California Angels | Baltimore Orioles | Trade |
| Dec 4, 1990 | Trade | Dave Gallagher | Baltimore Orioles | California Angels | Trade |
| Dec 4, 1990 | Trade | Eric King | Chicago White Sox | Cleveland Indians | Trade |
| Dec 4, 1990 | Trade | Shawn Hillegas | Chicago White Sox | Cleveland Indians | Trade |
| Dec 4, 1990 | Trade | Cory Snyder | Cleveland Indians | Chicago White Sox | Trade |
| Dec 4, 1990 | Trade | Lindsay Foster | Cleveland Indians | Chicago White Sox | Trade |
| Dec 4, 1990 | Trade | Darren Lewis | Oakland Athletics | San Francisco Giants | Trade |
| Dec 4, 1990 | Trade | Ernie Riles | San Francisco Giants | Oakland Athletics | Trade |
| Dec 3, 1990 | Released | Kevin Coffman | Chicago Cubs | — | Release |
| Dec 3, 1990 | Signed as free agent | Kevin Gross | — | Los Angeles Dodgers | Free agent signing |
| Dec 3, 1990 | Signed as free agent | Bill Gullickson | — | Detroit Tigers | Free agent signing |
| Dec 3, 1990 | Signed as free agent | Wayne Kirby | — | Cleveland Indians | Free agent signing |
| Dec 3, 1990 | Signed as free agent | Willie McGee | — | San Francisco Giants | Free agent signing |
| Dec 3, 1990 | Released | Dale Mohorcic | Montreal Expos | — | Release |
| Dec 3, 1990 | Signed as free agent | Terry Pendleton | — | Atlanta Braves | Free agent signing |
| Dec 3, 1990 | Released | Rolando Roomes | Montreal Expos | — | Release |
| Dec 3, 1990 | Released | Jeff Schulz | Kansas City Royals | — | Release |
| Dec 3, 1990 | Released | Mike Smith | Baltimore Orioles | — | Release |
| Dec 3, 1990 | Signed as free agent | Willie Wilson | — | Oakland Athletics | Free agent signing |
| Dec 3, 1990 | Trade | Oscar Azocar | New York Yankees | San Diego Padres | Trade |
| Dec 2, 1990 | Released | Roy Smith | Minnesota Twins | — | Release |
| Dec 2, 1990 | Trade | Junior Felix | Toronto Blue Jays | California Angels | Trade |
| Dec 2, 1990 | Trade | Luis Sojo | Toronto Blue Jays | California Angels | Trade |
| Dec 2, 1990 | Trade | Devon White | California Angels | Toronto Blue Jays | Trade |
| Dec 2, 1990 | Trade | Willie Fraser | California Angels | Toronto Blue Jays | Trade |
| Dec 2, 1990 | Trade | Marcus Moore | California Angels | Toronto Blue Jays | Trade |
| Dec 1, 1990 | Signed as free agent | Kirk Gibson | — | Kansas City Royals | Free agent signing |
| Dec 1990 | Signed as free agent | Johnny Paredes | — | Detroit Tigers | Free agent signing |
| Nov 30, 1990 | Released | Jerry Willard | Chicago White Sox | — | Release |
| Nov 28, 1990 | Signed as free agent | Jamie Quirk | — | Oakland Athletics | Free agent signing |
| Nov 26, 1990 | Signed as free agent | Ken Dayley | — | Toronto Blue Jays | Free agent signing |
| Nov 26, 1990 | Signed as free agent | Steve Farr | — | New York Yankees | Free agent signing |
| Nov 26, 1990 | Signed as free agent | Jose Segura | — | San Francisco Giants | Free agent signing |
| Nov 26, 1990 | Signed as free agent | John Shelby | — | Detroit Tigers | Free agent signing |
| Nov 25, 1990 | Signed as free agent | Rich Amaral | — | Seattle Mariners | Free agent signing |
| Nov 25, 1990 | Signed as free agent | Jose Escobar | — | Cleveland Indians | Free agent signing |
| Nov 23, 1990 | Signed as free agent | Rob Deer | — | Detroit Tigers | Free agent signing |
| Nov 21, 1990 | Signed as free agent | Mike Boddicker | — | Kansas City Royals | Free agent signing |
| Nov 21, 1990 | Signed as free agent | Tom Browning | — | Cincinnati Reds | Free agent signing |
| Nov 21, 1990 | Signed as free agent | Danny Jackson | — | Chicago Cubs | Free agent signing |
| Nov 21, 1990 | Signed | Ruben Rivera | — | New York Yankees | Amateur free agent signing |
| Nov 21, 1990 | Signed | Esteban Yan | — | Atlanta Braves | Amateur free agent signing |
| Nov 20, 1990 | Signed as free agent | Kevin Blankenship | — | Pittsburgh Pirates | Free agent signing |
| Nov 20, 1990 | Released | Jeff Stone | Boston Red Sox | — | Release |
| Nov 19, 1990 | Released | Brian Dorsett | New York Yankees | — | Release |
| Nov 19, 1990 | Signed as free agent | Dan Gakeler | — | Detroit Tigers | Free agent signing |
| Nov 19, 1990 | Signed as free agent | Tim Leary | — | New York Yankees | Free agent signing |
| Nov 19, 1990 | Trade | Paul Williams | Boston Red Sox | New York Mets | Trade |
| Nov 16, 1990 | Signed as free agent | Chito Martinez | — | Baltimore Orioles | Free agent signing |
| Nov 15, 1990 | Signed as free agent | Scott Service | — | Montreal Expos | Free agent signing |
| Nov 15, 1990 | Signed as free agent | Steve Springer | — | Seattle Mariners | Free agent signing |
| Nov 13, 1990 | Released | Marty Clary | Atlanta Braves | — | Release |
| Nov 13, 1990 | Signed | Giomar Guevara | — | Seattle Mariners | Amateur free agent signing |
| Nov 13, 1990 | Released | Dwayne Henry | Atlanta Braves | — | Release |
| Nov 13, 1990 | Released | Keith Hughes | New York Mets | — | Release |
| Nov 13, 1990 | Released | Chris Jelic | New York Mets | — | Release |
| Nov 13, 1990 | Released | Jamie Moyer | Texas Rangers | — | Release |
| Nov 11, 1990 | Signed | Cameron Cairncross | — | San Diego Padres | Amateur free agent signing |
| Nov 9, 1990 | Signed as free agent | Buddy Black | — | San Francisco Giants | Free agent signing |
| Nov 9, 1990 | Trade | Brian Harrison | San Diego Padres | Montreal Expos | Trade |
| Nov 9, 1990 | Trade | John Costello | Montreal Expos | San Diego Padres | Trade |
| Nov 8, 1990 | Signed as free agent | Darryl Strawberry | — | Los Angeles Dodgers | Free agent signing |
| Nov 6, 1990 | Signed as free agent | Dave Liddell | — | Cincinnati Reds | Free agent signing |
| Nov 6, 1990 | Trade | Willie Blair | Toronto Blue Jays | Cleveland Indians | Trade |
| Nov 6, 1990 | Trade | Alex Sanchez | Cleveland Indians | Toronto Blue Jays | Trade |
| Nov 6, 1990 | Trade | Earl Sanders | Toronto Blue Jays | Atlanta Braves | Trade |
| Nov 6, 1990 | Trade | Nate Cromwell | Atlanta Braves | Toronto Blue Jays | Trade |
| Nov 5, 1990 | Released | Donnie Hill | California Angels | — | Release |
| Nov 5, 1990 | Released | Jamie Quirk | Oakland Athletics | — | Release |
| Nov 5, 1990 | Signed as free agent | Matt Sinatro | — | Seattle Mariners | Free agent signing |
| Nov 2, 1990 | Signed as free agent | Rick Wrona | — | Milwaukee Brewers | Free agent signing |
| Nov 1, 1990 | Released | Scott Anderson | Montreal Expos | — | Release |
| Nov 1, 1990 | Signed as free agent | Tim Scott | — | San Diego Padres | Free agent signing |
| Oct 30, 1990 | Released | Dion James | Cleveland Indians | — | Release |
| Oct 29, 1990 | Trade | Lee Johnson | Atlanta Braves | Houston Astros | Trade |
| Oct 26, 1990 | Released | Rick Luecken | Toronto Blue Jays | — | Release |
| Oct 25, 1990 | Released | Mike Laga | San Francisco Giants | — | Release |
| Oct 24, 1990 | Released | Jim Eppard | Toronto Blue Jays | — | Release |
| Oct 24, 1990 | Released | Dwight Evans | Boston Red Sox | — | Release |
| Oct 22, 1990 | Released | Keith Shepherd | Cleveland Indians | — | Release |
| Oct 16, 1990 | Released | Mike Birkbeck | Milwaukee Brewers | — | Release |
| Oct 16, 1990 | Released | Tom Filer | Milwaukee Brewers | — | Release |
| Oct 15, 1990 | Released | Ernie Whitt | Atlanta Braves | — | Release |
| Oct 14, 1990 | Signed as free agent | Eric Bell | — | Cleveland Indians | Free agent signing |
| Oct 12, 1990 | Signed | Jose Cabrera | — | Cleveland Indians | Amateur free agent signing |
| Oct 12, 1990 | Released | Jeffrey Leonard | Seattle Mariners | — | Release |
| Oct 11, 1990 | Released | Ernie Camacho | St. Louis Cardinals | — | Release |
| Oct 11, 1990 | Released | Stan Clarke | St. Louis Cardinals | — | Release |
| Oct 11, 1990 | Released | Bill Schroeder | California Angels | — | Release |
| Oct 10, 1990 | Released | Dorn Taylor | Baltimore Orioles | — | Release |
| Oct 5, 1990 | Signed | Einar Diaz | — | Cleveland Indians | Amateur free agent signing |
| Oct 5, 1990 | Released | Wayne Tolleson | New York Yankees | — | Release |
| Oct 4, 1990 | Released | Bill Bathe | San Francisco Giants | — | Release |
| Oct 4, 1990 | Released | Chris Codiroli | Kansas City Royals | — | Release |
| Oct 4, 1990 | Released | Pete Filson | Kansas City Royals | — | Release |
| Oct 4, 1990 | Released | Bill Gullickson | Houston Astros | — | Release |
| Oct 4, 1990 | Released | Al Nipper | Cleveland Indians | — | Release |
| Oct 4, 1990 | Released | Rey Palacios | Kansas City Royals | — | Release |
| Oct 4, 1990 | Released | Claudell Washington | New York Yankees | — | Release |
| Oct 3, 1990 | Released | Randy O'Neal | San Francisco Giants | — | Release |
| Oct 3, 1990 | Released | Johnny Paredes | Montreal Expos | — | Release |
| Oct 1, 1990 | Released | Tommy Barrett | Philadelphia Phillies | — | Release |
| Oct 1, 1990 | Released | Bob Sebra | Milwaukee Brewers | — | Release |
| Sep 30, 1990 | Released | Jody Davis | Detroit Tigers | — | Release |
| Sep 30, 1990 | Trade | Mike Wilkins | Detroit Tigers | Los Angeles Dodgers | Trade |
| Sep 30, 1990 | Trade | Mike Munoz | Los Angeles Dodgers | Detroit Tigers | Trade |
| Sep 28, 1990 | Trade | Tony Longmire | Pittsburgh Pirates | Philadelphia Phillies | Trade |
| Sep 28, 1990 | Trade | Mike Pomeranz | Pittsburgh Pirates | Chicago Cubs | Trade |
| Sep 27, 1990 | Signed as free agent | Mark Bailey | — | San Francisco Giants | Free agent signing |
| Sep 27, 1990 | Released | Mike Brumley | Seattle Mariners | — | Release |
| Sep 26, 1990 | Trade | Ed Gustafson | San Francisco Giants | Minnesota Twins | Trade |
| Sep 24, 1990 | Signed | Rob Butler | — | Toronto Blue Jays | Amateur free agent signing |
| Sep 24, 1990 | Signed | Rich Butler | — | Toronto Blue Jays | Amateur free agent signing |
| Sep 24, 1990 | Released | Deion Sanders | New York Yankees | — | Release |
| Sep 24, 1990 | Trade | Alex Sanchez | Toronto Blue Jays | Cleveland Indians | Trade |
| Sep 21, 1990 | Released | Mark Clear | Chicago Cubs | — | Release |
| Sep 21, 1990 | Signed as free agent | Barry Lyons | — | Los Angeles Dodgers | Free agent signing |
| Sep 21, 1990 | Released | Tom Thobe | Chicago Cubs | — | Release |
| Sep 21, 1990 | Trade | Steve Cummings | Toronto Blue Jays | Cleveland Indians | Trade |
| Sep 20, 1990 | Signed | Miguel Cairo | — | Los Angeles Dodgers | Amateur free agent signing |
| Sep 18, 1990 | Released | Rich Renteria | Seattle Mariners | — | Release |
| Sep 17, 1990 | Signed | Jose Paniagua | — | Montreal Expos | Amateur free agent signing |
| Sep 16, 1990 | Trade | Mauro Gozzo | Toronto Blue Jays | Cleveland Indians | Trade |
| Sep 16, 1990 | Trade | Buddy Black | Cleveland Indians | Toronto Blue Jays | Trade |
| Sep 13, 1990 | Trade | Darrin Fletcher | Los Angeles Dodgers | Philadelphia Phillies | Trade |
| Sep 13, 1990 | Trade | Dennis Cook | Philadelphia Phillies | Los Angeles Dodgers | Trade |
| Sep 11, 1990 | Trade | Kevin Carmody | Milwaukee Brewers | New York Mets | Trade |
| Sep 10, 1990 | Trade | Steve Larose | New York Mets | Houston Astros | Trade |
| Sep 10, 1990 | Trade | Nick Davis | New York Mets | Houston Astros | Trade |
| Sep 10, 1990 | Trade | Dan Schatzeder | Houston Astros | New York Mets | Trade |
| Sep 7, 1990 | Signed | Guillermo Mota | — | New York Mets | Amateur free agent signing |
| Sep 7, 1990 | Trade | Julio Machado | New York Mets | Milwaukee Brewers | Trade |
| Sep 7, 1990 | Trade | Kevin Brown | New York Mets | Milwaukee Brewers | Trade |
| Sep 7, 1990 | Trade | Terry McGriff | Cincinnati Reds | Houston Astros | Trade |
| Sep 7, 1990 | Trade | Keith Kaiser | Cincinnati Reds | Houston Astros | Trade |
| Sep 7, 1990 | Trade | Butch Henry | Cincinnati Reds | Houston Astros | Trade |
| Sep 7, 1990 | Trade | Lloyd McClendon | Chicago Cubs | Pittsburgh Pirates | Trade |
| Sep 6, 1990 | Signed | Ramon Tatis | — | New York Mets | Amateur free agent signing |
| Sep 5, 1990 | Released | Ricky Horton | Milwaukee Brewers | — | Release |
| Sep 5, 1990 | Trade | Dorn Taylor | Pittsburgh Pirates | Baltimore Orioles | Trade |
| Sep 4, 1990 | Released | Barry Lyons | New York Mets | — | Release |
| Sep 4, 1990 | Released | Randy St. Claire | Texas Rangers | — | Release |
| Sep 4, 1990 | Released | Rich Thompson | Montreal Expos | — | Release |
| Sep 4, 1990 | Trade | Victor Rosario | Philadelphia Phillies | Atlanta Braves | Trade |
| Sep 4, 1990 | Trade | Joe Bitker | Oakland Athletics | Texas Rangers | Trade |
| Sep 4, 1990 | Trade | Scott Chiamparino | Oakland Athletics | Texas Rangers | Trade |
| Sep 1, 1990 | Trade | Randy Kramer | Pittsburgh Pirates | Chicago Cubs | Trade |
| Sep 1, 1990 | Trade | Greg Kallevig | Chicago Cubs | Pittsburgh Pirates | Trade |
| Aug 30, 1990 | Trade | Wes Chamberlain | Pittsburgh Pirates | Philadelphia Phillies | Trade |
| Aug 30, 1990 | Trade | Julio Peguero | Pittsburgh Pirates | Philadelphia Phillies | Trade |
| Aug 30, 1990 | Trade | Carmelo Martinez | Philadelphia Phillies | Pittsburgh Pirates | Trade |
| Aug 30, 1990 | Trade | Archie Corbin | New York Mets | Kansas City Royals | Trade |
| Aug 30, 1990 | Trade | Pat Tabler | Kansas City Royals | New York Mets | Trade |
| Aug 30, 1990 | Trade | Rocky Elli | New York Mets | Philadelphia Phillies | Trade |
| Aug 30, 1990 | Trade | Nikco Riesgo | New York Mets | Philadelphia Phillies | Trade |
| Aug 30, 1990 | Trade | Tom Herr | Philadelphia Phillies | New York Mets | Trade |
| Aug 30, 1990 | Trade | Charlie O'Brien | Milwaukee Brewers | New York Mets | Trade |
| Aug 30, 1990 | Trade | Larry Andersen | Houston Astros | Boston Red Sox | Trade |
| Aug 30, 1990 | Trade | Jeff Bagwell | Boston Red Sox | Houston Astros | Trade |
| Aug 30, 1990 | Trade | Bill Doran | Houston Astros | Cincinnati Reds | Trade |
| Aug 29, 1990 | Signed as free agent | Ken Griffey | — | Seattle Mariners | Free agent signing |
| Aug 29, 1990 | Trade | Harold Baines | Texas Rangers | Oakland Athletics | Trade |
| Aug 29, 1990 | Trade | Felix Jose | Oakland Athletics | St. Louis Cardinals | Trade |
| Aug 29, 1990 | Trade | Stan Royer | Oakland Athletics | St. Louis Cardinals | Trade |
| Aug 29, 1990 | Trade | Daryl Green | Oakland Athletics | St. Louis Cardinals | Trade |
| Aug 29, 1990 | Trade | Willie McGee | St. Louis Cardinals | Oakland Athletics | Trade |
| Aug 28, 1990 | Released | Brian Fisher | Houston Astros | — | Release |
| Aug 28, 1990 | Signed as free agent | Wallace Johnson | — | Oakland Athletics | Free agent signing |
| Aug 28, 1990 | Released | Doug Sisk | Atlanta Braves | — | Release |
| Aug 26, 1990 | Signed | Arquimedez Pozo | — | Seattle Mariners | Amateur free agent signing |
| Aug 25, 1990 | Signed | Cory Lidle | — | Minnesota Twins | Amateur free agent signing |
| Aug 24, 1990 | Signed | Omar Daal | — | Los Angeles Dodgers | Amateur free agent signing |
| Aug 24, 1990 | Released | Ken Griffey | Cincinnati Reds | — | Release |
| Aug 24, 1990 | Signed as free agent | Atlee Hammaker | — | San Diego Padres | Free agent signing |
| Aug 23, 1990 | Signed as free agent | Cecilio Guante | — | Boston Red Sox | Free agent signing |
| Aug 21, 1990 | Signed | Bobby Abreu | — | Houston Astros | Amateur free agent signing |
| Aug 18, 1990 | Signed as free agent | John Hoover | — | Montreal Expos | Free agent signing |
| Aug 17, 1990 | Trade | Mark McLemore | California Angels | Cleveland Indians | Trade |
| Aug 16, 1990 | Signed as free agent | Billy Taylor | — | Atlanta Braves | Free agent signing |
| Aug 16, 1990 | Trade | Moises Alou | Pittsburgh Pirates | Montreal Expos | Trade |
| Aug 14, 1990 | Released | Matt Kinzer | Baltimore Orioles | — | Release |
| Aug 12, 1990 | Released | Cecilio Guante | Cleveland Indians | — | Release |
| Aug 12, 1990 | Released | Atlee Hammaker | San Francisco Giants | — | Release |
| Aug 12, 1990 | Released | Jerry Reed | Boston Red Sox | — | Release |
| Aug 11, 1990 | Released | Wallace Johnson | Montreal Expos | — | Release |
| Aug 10, 1990 | Signed as free agent | Ricky Horton | — | Milwaukee Brewers | Free agent signing |
| Aug 9, 1990 | Trade | Jim Vatcher | Philadelphia Phillies | Atlanta Braves | Trade |
| Aug 9, 1990 | Trade | Tommy Greene | Atlanta Braves | Philadelphia Phillies | Trade |
| Aug 8, 1990 | Released | Fred Manrique | Minnesota Twins | — | Release |
| Aug 8, 1990 | Trade | Scott Ruskin | Pittsburgh Pirates | Montreal Expos | Trade |
| Aug 8, 1990 | Trade | Willie Greene | Pittsburgh Pirates | Montreal Expos | Trade |
| Aug 8, 1990 | Trade | Zane Smith | Montreal Expos | Pittsburgh Pirates | Trade |
| Aug 3, 1990 | Signed as free agent | Matt Kinzer | — | Baltimore Orioles | Free agent signing |
| Aug 3, 1990 | Signed as free agent | Alex Trevino | — | New York Mets | Free agent signing |
| Aug 3, 1990 | Trade | Jeff Parrett | Philadelphia Phillies | Atlanta Braves | Trade |
| Aug 3, 1990 | Trade | Dale Murphy | Atlanta Braves | Philadelphia Phillies | Trade |
| Aug 1, 1990 | Released | Ron Coomer | Oakland Athletics | — | Release |
| Aug 1, 1990 | Signed as free agent | Steve Springer | — | San Diego Padres | Free agent signing |
| Jul 31, 1990 | Released | Shawn Barton | Atlanta Braves | — | Release |
| Jul 31, 1990 | Signed as free agent | Joe Hesketh | — | Boston Red Sox | Free agent signing |
| Jul 31, 1990 | Released | Steve Springer | Cleveland Indians | — | Release |
| Jul 30, 1990 | Trade | Ron Kittle | Chicago White Sox | Baltimore Orioles | Trade |
| Jul 30, 1990 | Trade | Phil Bradley | Baltimore Orioles | Chicago White Sox | Trade |
| Jul 28, 1990 | Signed as free agent | Walt Terrell | — | Detroit Tigers | Free agent signing |
| Jul 27, 1990 | Signed as free agent | Charlie Kerfeld | — | Atlanta Braves | Free agent signing |
| Jul 27, 1990 | Released | Alex Trevino | Houston Astros | — | Release |
| Jul 27, 1990 | Trade | Greg Hansell | Boston Red Sox | New York Mets | Trade |
| Jul 27, 1990 | Trade | Ed Perozo | Boston Red Sox | New York Mets | Trade |
| Jul 27, 1990 | Trade | Mike Marshall | New York Mets | Boston Red Sox | Trade |
| Jul 27, 1990 | Trade | Nelson Liriano | Toronto Blue Jays | Minnesota Twins | Trade |
| Jul 27, 1990 | Trade | Pedro Munoz | Toronto Blue Jays | Minnesota Twins | Trade |
| Jul 27, 1990 | Trade | John Candelaria | Minnesota Twins | Toronto Blue Jays | Trade |
| Jul 25, 1990 | Released | Ricky Horton | St. Louis Cardinals | — | Release |
| Jul 24, 1990 | Released | Joe Hesketh | Atlanta Braves | — | Release |
| Jul 24, 1990 | Released | Walt Terrell | Pittsburgh Pirates | — | Release |
| Jul 23, 1990 | Released | Charlie Kerfeld | Atlanta Braves | — | Release |
| Jul 23, 1990 | Trade | Marvin Freeman | Philadelphia Phillies | Atlanta Braves | Trade |
| Jul 23, 1990 | Trade | Joe Boever | Atlanta Braves | Philadelphia Phillies | Trade |
| Jul 22, 1990 | Released | Tom Lawless | Toronto Blue Jays | — | Release |
| Jul 22, 1990 | Trade | Tony Valle | Atlanta Braves | New York Mets | Trade |
| Jul 22, 1990 | Trade | Doug Sisk | New York Mets | Atlanta Braves | Trade |
| Jul 21, 1990 | Released | John Hoover | Texas Rangers | — | Release |
| Jul 16, 1990 | Signed as free agent | Rich Sauveur | — | Montreal Expos | Free agent signing |
| Jul 15, 1990 | Released | Mike Norris | Oakland Athletics | — | Release |
| Jul 15, 1990 | Released | Ed Romero | Detroit Tigers | — | Release |
| Jul 12, 1990 | Released | Matt Kinzer | Detroit Tigers | — | Release |
| Jul 12, 1990 | Trade | Mark Grant | San Diego Padres | Atlanta Braves | Trade |
| Jul 12, 1990 | Trade | Derek Lilliquist | Atlanta Braves | San Diego Padres | Trade |
| Jul 12, 1990 | Trade | Greg Edge | Milwaukee Brewers | Pittsburgh Pirates | Trade |
| Jul 12, 1990 | Trade | Jim Czajkowski | Pittsburgh Pirates | Milwaukee Brewers | Trade |
| Jul 11, 1990 | Trade | Tom Lampkin | Cleveland Indians | San Diego Padres | Trade |
| Jul 11, 1990 | Trade | Alex Cole | San Diego Padres | Cleveland Indians | Trade |
| Jul 7, 1990 | Signed as free agent | Jerry Reuss | — | Pittsburgh Pirates | Free agent signing |
| Jul 7, 1990 | Released | Eddie Zambrano | Cleveland Indians | — | Release |
| Jul 4, 1990 | Signed as free agent | Louie Meadows | — | Philadelphia Phillies | Free agent signing |
| Jul 3, 1990 | Signed | Jolbert Cabrera | — | Montreal Expos | Amateur free agent signing |
| Jul 3, 1990 | Signed | Hanley Frias | — | Texas Rangers | Amateur free agent signing |
| Jul 3, 1990 | Released | Greg Walker | Baltimore Orioles | — | Release |
| Jul 2, 1990 | Signed | Israel Alcantara | — | Montreal Expos | Amateur free agent signing |
| Jul 2, 1990 | Signed as free agent | Ernie Camacho | — | St. Louis Cardinals | Free agent signing |
| Jul 2, 1990 | Signed | Ugueth Urbina | — | Montreal Expos | Amateur free agent signing |
| Jul 1990 | Trade | Dwight Taylor | Cleveland Indians | Atlanta Braves | Trade |
| Jun 28, 1990 | Signed | John O'Donoghue | — | Baltimore Orioles | Amateur free agent signing |
| Jun 26, 1990 | Released | Bob Knepper | San Francisco Giants | — | Release |
| Jun 26, 1990 | Trade | Steve Hecht | San Francisco Giants | Montreal Expos | Trade |
| Jun 25, 1990 | Trade | Jay Tibbs | Baltimore Orioles | Pittsburgh Pirates | Trade |
| Jun 24, 1990 | Signed as free agent | Rick Rodriguez | — | San Francisco Giants | Free agent signing |
| Jun 23, 1990 | Released | Ernie Camacho | San Francisco Giants | — | Release |
| Jun 22, 1990 | Signed as free agent | Mark Clear | — | Chicago Cubs | Free agent signing |
| Jun 22, 1990 | Released | Jim Dwyer | Minnesota Twins | — | Release |
| Jun 21, 1990 | Released | Richard Dotson | Kansas City Royals | — | Release |
| Jun 21, 1990 | Signed as free agent | Jim Tatum | — | Milwaukee Brewers | Free agent signing |
| Jun 19, 1990 | Signed as free agent | Shawn Barton | — | Atlanta Braves | Free agent signing |
| Jun 19, 1990 | Signed | Steve Phoenix | — | Oakland Athletics | Amateur free agent signing |
| Jun 19, 1990 | Trade | Brian Givens | New York Mets | Seattle Mariners | Trade |
| Jun 19, 1990 | Trade | Mario Diaz | Seattle Mariners | New York Mets | Trade |
| Jun 18, 1990 | Trade | Tracy Jones | Detroit Tigers | Seattle Mariners | Trade |
| Jun 18, 1990 | Trade | Darnell Coles | Seattle Mariners | Detroit Tigers | Trade |
| Jun 16, 1990 | Released | Mike Davis | San Francisco Giants | — | Release |
| Jun 15, 1990 | Signed as free agent | Jeff Schwarz | — | Milwaukee Brewers | Free agent signing |
| Jun 14, 1990 | Released | Shawn Barton | New York Mets | — | Release |
| Jun 14, 1990 | Signed as free agent | Randy St. Claire | — | Texas Rangers | Free agent signing |
| Jun 13, 1990 | Signed | Darryl Scott | — | California Angels | Amateur free agent signing |
| Jun 13, 1990 | Signed as free agent | John Shelby | — | Detroit Tigers | Free agent signing |
| Jun 12, 1990 | Signed as free agent | Doug Sisk | — | New York Mets | Free agent signing |
| Jun 11, 1990 | Signed as free agent | Doug Strange | — | Chicago Cubs | Free agent signing |
| Jun 11, 1990 | Trade | Daven Bond | Houston Astros | New York Yankees | Trade |
| Jun 9, 1990 | Signed as free agent | Steve Lombardozzi | — | Detroit Tigers | Free agent signing |
| Jun 9, 1990 | Released | Doug Sisk | Cleveland Indians | — | Release |
| Jun 9, 1990 | Trade | Glenn Braggs | Milwaukee Brewers | Cincinnati Reds | Trade |
| Jun 9, 1990 | Trade | Billy Bates | Milwaukee Brewers | Cincinnati Reds | Trade |
| Jun 9, 1990 | Trade | Ron Robinson | Cincinnati Reds | Milwaukee Brewers | Trade |
| Jun 9, 1990 | Trade | Bob Sebra | Cincinnati Reds | Milwaukee Brewers | Trade |
| Jun 8, 1990 | Signed as free agent | Mike Davis | — | San Francisco Giants | Free agent signing |
| Jun 6, 1990 | Released | Mark Clear | California Angels | — | Release |
| Jun 6, 1990 | Released | Chris Howard | Cleveland Indians | — | Release |
| Jun 6, 1990 | Trade | Frank Bolick | Milwaukee Brewers | Seattle Mariners | Trade |
| Jun 6, 1990 | Trade | Mickey Brantley | Seattle Mariners | Milwaukee Brewers | Trade |
| Jun 5, 1990 | Released | Bill Buckner | Boston Red Sox | — | Release |
| Jun 4, 1990 | Trade | Lance McCullers | New York Yankees | Detroit Tigers | Trade |
| Jun 4, 1990 | Trade | Clay Parker | New York Yankees | Detroit Tigers | Trade |
| Jun 4, 1990 | Trade | Matt Nokes | Detroit Tigers | New York Yankees | Trade |
| Jun 2, 1990 | Released | Thad Bosley | Texas Rangers | — | Release |
| Jun 2, 1990 | Released | John Shelby | Los Angeles Dodgers | — | Release |
| Jun 1, 1990 | Signed | Angelo Encarnacion | — | Pittsburgh Pirates | Amateur free agent signing |
| Jun 1990 | Signed as free agent | Chris Codiroli | — | Kansas City Royals | Free agent signing |
| May 30, 1990 | Trade | Francisco Oliveras | Minnesota Twins | San Francisco Giants | Trade |
| May 28, 1990 | Signed as free agent | Jody Davis | — | Detroit Tigers | Free agent signing |
| May 28, 1990 | Released | Steve Lombardozzi | Houston Astros | — | Release |
| May 25, 1990 | Signed as free agent | Jeff Bronkey | — | Texas Rangers | Free agent signing |
| May 25, 1990 | Released | Doug Strange | Houston Astros | — | Release |
| May 25, 1990 | Signed as free agent | Freddie Toliver | — | California Angels | Free agent signing |
| May 24, 1990 | Released | Jim Tatum | Cleveland Indians | — | Release |
| May 24, 1990 | Trade | Russ Swan | San Francisco Giants | Seattle Mariners | Trade |
| May 24, 1990 | Trade | Gary Eave | Seattle Mariners | San Francisco Giants | Trade |
| May 23, 1990 | Signed as free agent | Mark Lee | — | Milwaukee Brewers | Free agent signing |
| May 22, 1990 | Signed as free agent | Mike Raczka | — | Oakland Athletics | Free agent signing |
| May 19, 1990 | Signed | Dario Veras | — | Los Angeles Dodgers | Amateur free agent signing |
| May 18, 1990 | Signed as free agent | Roger Mason | — | Pittsburgh Pirates | Free agent signing |
| May 18, 1990 | Trade | Lee Hancock | Seattle Mariners | Pittsburgh Pirates | Trade |
| May 18, 1990 | Trade | Scott Medvin | Pittsburgh Pirates | Seattle Mariners | Trade |
| May 16, 1990 | Released | Jody Davis | Atlanta Braves | — | Release |
| May 14, 1990 | Released | Larry McWilliams | Kansas City Royals | — | Release |
| May 14, 1990 | Released | Jerry Reuss | Houston Astros | — | Release |
| May 13, 1990 | Trade | Stan Javier | Oakland Athletics | Los Angeles Dodgers | Trade |
| May 13, 1990 | Trade | Willie Randolph | Los Angeles Dodgers | Oakland Athletics | Trade |
| May 11, 1990 | Signed | Olmedo Saenz | — | Chicago White Sox | Amateur free agent signing |
| May 11, 1990 | Trade | Dave Winfield | New York Yankees | California Angels | Trade |
| May 11, 1990 | Trade | Mike Witt | California Angels | New York Yankees | Trade |
| May 10, 1990 | Signed as free agent | Chris Howard | — | Cleveland Indians | Free agent signing |
| May 10, 1990 | Signed as free agent | Craig McMurtry | — | Texas Rangers | Free agent signing |
| May 9, 1990 | Signed as free agent | Andy McGaffigan | — | Kansas City Royals | Free agent signing |
| May 8, 1990 | Released | Andy Allanson | Texas Rangers | — | Release |
| May 8, 1990 | Released | Mike Flanagan | Toronto Blue Jays | — | Release |
| May 8, 1990 | Signed as free agent | John Russell | — | Texas Rangers | Free agent signing |
| May 7, 1990 | Signed as free agent | Dennis Powell | — | Milwaukee Brewers | Free agent signing |
| May 5, 1990 | Signed as free agent | Terry Francona | — | St. Louis Cardinals | Free agent signing |
| May 4, 1990 | Signed as free agent | Greg Walker | — | Baltimore Orioles | Free agent signing |
| May 4, 1990 | Trade | Lee Smith | Boston Red Sox | St. Louis Cardinals | Trade |
| May 4, 1990 | Trade | Tom Brunansky | St. Louis Cardinals | Boston Red Sox | Trade |
| May 3, 1990 | Signed as free agent | Jerry Reed | — | Boston Red Sox | Free agent signing |
| May 2, 1990 | Released | Mike Raczka | San Diego Padres | — | Release |
| May 2, 1990 | Trade | Greg Tubbs | Atlanta Braves | Pittsburgh Pirates | Trade |
| May 2, 1990 | Trade | Rico Rossy | Pittsburgh Pirates | Atlanta Braves | Trade |
| May 1, 1990 | Signed as free agent | John Davis | — | San Diego Padres | Free agent signing |
| May 1, 1990 | Released | Chris Howard | New York Yankees | — | Release |
| Apr 30, 1990 | Released | Greg Walker | Chicago White Sox | — | Release |
| Apr 30, 1990 | Trade | Frank Campos | Chicago Cubs | Chicago White Sox | Trade |
| Apr 30, 1990 | Trade | Bill Long | Chicago White Sox | Chicago Cubs | Trade |
| Apr 29, 1990 | Trade | Luis Polonia | New York Yankees | California Angels | Trade |
| Apr 29, 1990 | Trade | Claudell Washington | California Angels | New York Yankees | Trade |
| Apr 29, 1990 | Trade | Rich Monteleone | California Angels | New York Yankees | Trade |
| Apr 28, 1990 | Signed | Marino Santana | — | Seattle Mariners | Amateur free agent signing |
| Apr 28, 1990 | Trade | Kevin Dean | Atlanta Braves | Houston Astros | Trade |
| Apr 28, 1990 | Trade | Charlie Kerfeld | Houston Astros | Atlanta Braves | Trade |
| Apr 27, 1990 | Released | Terry Francona | Milwaukee Brewers | — | Release |
| Apr 27, 1990 | Released | Jeff Schwarz | Baltimore Orioles | — | Release |
| Apr 26, 1990 | Released | John Davis | Milwaukee Brewers | — | Release |
| Apr 25, 1990 | Released | Andy McGaffigan | San Francisco Giants | — | Release |
| Apr 25, 1990 | Released | Craig McMurtry | Texas Rangers | — | Release |
| Apr 25, 1990 | Released | Jerry Reed | Seattle Mariners | — | Release |
| Apr 25, 1990 | Released | Rafael Santana | Cleveland Indians | — | Release |
| Apr 25, 1990 | Signed as free agent | Pat Sheridan | — | Chicago Cubs | Free agent signing |
| Apr 25, 1990 | Signed as free agent | Chico Walker | — | Chicago Cubs | Free agent signing |
| Apr 23, 1990 | Trade | Rex Hudler | Montreal Expos | St. Louis Cardinals | Trade |
| Apr 23, 1990 | Trade | John Costello | St. Louis Cardinals | Montreal Expos | Trade |
| Apr 17, 1990 | Signed | Rich Batchelor | — | New York Yankees | Amateur free agent signing |
| Apr 17, 1990 | Trade | Alan Cockrell | Minnesota Twins | Cleveland Indians | Trade |
| Apr 17, 1990 | Trade | Charlie Scott | Cleveland Indians | Minnesota Twins | Trade |
| Apr 16, 1990 | Signed as free agent | Donell Nixon | — | Baltimore Orioles | Free agent signing |
| Apr 14, 1990 | Signed as free agent | Mike Kingery | — | San Francisco Giants | Free agent signing |
| Apr 14, 1990 | Signed as free agent | Jerry Reuss | — | Houston Astros | Free agent signing |
| Apr 13, 1990 | Signed as free agent | Paul Zuvella | — | Kansas City Royals | Free agent signing |
| Apr 13, 1990 | Trade | Unnamed | Minnesota Twins | Texas Rangers | $ |
| Apr 13, 1990 | Trade | Jeff Satzinger | Minnesota Twins | Texas Rangers | Trade |
| Apr 13, 1990 | Trade | Fred Manrique | Texas Rangers | Minnesota Twins | Trade |
| Apr 11, 1990 | Signed as free agent | Jeff Kaiser | — | Cleveland Indians | Free agent signing |
| Apr 10, 1990 | Signed as free agent | Tom Niedenfuer | — | St. Louis Cardinals | Free agent signing |
| Apr 10, 1990 | Trade | Brian Morrison | Toronto Blue Jays | Pittsburgh Pirates | Trade |
| Apr 10, 1990 | Trade | Joe Szekely | Pittsburgh Pirates | Toronto Blue Jays | Trade |
| Apr 9, 1990 | Signed as free agent | Jeff Fassero | — | Cleveland Indians | Free agent signing |
| Apr 8, 1990 | Signed as free agent | Rick Leach | — | San Francisco Giants | Free agent signing |
| Apr 8, 1990 | Signed as free agent | Urbano Lugo | — | Detroit Tigers | Free agent signing |
| Apr 8, 1990 | Signed as free agent | Paul Mirabella | — | Milwaukee Brewers | Free agent signing |
| Apr 8, 1990 | Released | Donell Nixon | San Francisco Giants | — | Release |
| Apr 8, 1990 | Signed as free agent | Mark Salas | — | Detroit Tigers | Free agent signing |
| Apr 7, 1990 | Signed as free agent | John Davis | — | Milwaukee Brewers | Free agent signing |
| Apr 7, 1990 | Signed as free agent | Jeff Gray | — | Boston Red Sox | Free agent signing |
| Apr 7, 1990 | Signed as free agent | Terry Leach | — | Minnesota Twins | Free agent signing |
| Apr 7, 1990 | Trade | Andy McGaffigan | Montreal Expos | San Francisco Giants | Trade |
| Apr 6, 1990 | Signed as free agent | Mike Brumley | — | Seattle Mariners | Free agent signing |
| Apr 6, 1990 | Released | Tom Niedenfuer | Seattle Mariners | — | Release |
| Apr 6, 1990 | Signed as free agent | Dickie Noles | — | Philadelphia Phillies | Free agent signing |
| Apr 6, 1990 | Released | John Russell | Atlanta Braves | — | Release |
| Apr 6, 1990 | Signed | Carlos Valdez | — | San Francisco Giants | Amateur free agent signing |
| Apr 5, 1990 | Signed as free agent | Greg Booker | — | San Francisco Giants | Free agent signing |
| Apr 5, 1990 | Signed as free agent | Bob Knepper | — | San Francisco Giants | Free agent signing |
| Apr 5, 1990 | Trade | Robert Fletcher | Chicago White Sox | Montreal Expos | Trade |
| Apr 5, 1990 | Trade | Mike Campbell | Montreal Expos | Chicago White Sox | Trade |
| Apr 4, 1990 | Released | Darrell Evans | Atlanta Braves | — | Release |
| Apr 4, 1990 | Trade | Mike Pomeranz | Minnesota Twins | Pittsburgh Pirates | Trade |
| Apr 4, 1990 | Trade | Junior Ortiz | Pittsburgh Pirates | Minnesota Twins | Trade |
| Apr 4, 1990 | Trade | Orlando Lind | Pittsburgh Pirates | Minnesota Twins | Trade |
| Apr 3, 1990 | Released | Joaquin Andujar | Montreal Expos | — | Release |
| Apr 3, 1990 | Released | Greg Booker | Chicago Cubs | — | Release |
| Apr 3, 1990 | Released | Mike Brumley | Baltimore Orioles | — | Release |
| Apr 3, 1990 | Released | Jeff Fassero | Chicago White Sox | — | Release |
| Apr 3, 1990 | Released | Roger Mason | Houston Astros | — | Release |
| Apr 3, 1990 | Signed as free agent | Brett Merriman | — | California Angels | Free agent signing |
| Apr 3, 1990 | Released | Jerry Reuss | Chicago White Sox | — | Release |
| Apr 3, 1990 | Released | Pat Sheridan | Kansas City Royals | — | Release |
| Apr 3, 1990 | Trade | Mike Roesler | Cincinnati Reds | Pittsburgh Pirates | Trade |
| Apr 3, 1990 | Trade | Jeff Richardson | Cincinnati Reds | Pittsburgh Pirates | Trade |
| Apr 3, 1990 | Trade | Billy Hatcher | Pittsburgh Pirates | Cincinnati Reds | Trade |
| Apr 2, 1990 | Signed as free agent | Andy Allanson | — | Texas Rangers | Free agent signing |
| Apr 2, 1990 | Released | John Davis | Chicago White Sox | — | Release |
| Apr 2, 1990 | Released | Denny Gonzalez | Cleveland Indians | — | Release |
| Apr 2, 1990 | Released | Wayne Housie | Detroit Tigers | — | Release |
| Apr 2, 1990 | Released | Terry Leach | Kansas City Royals | — | Release |
| Apr 2, 1990 | Released | Freddie Toliver | New York Yankees | — | Release |
| Apr 2, 1990 | Released | Paul Zuvella | Cleveland Indians | — | Release |
| Apr 2, 1990 | Trade | Chuck Everson | Detroit Tigers | Kansas City Royals | Trade |
| Apr 2, 1990 | Trade | Jerry Don Gleaton | Kansas City Royals | Detroit Tigers | Trade |
| Apr 2, 1990 | Trade | Jeff Huson | Montreal Expos | Texas Rangers | Trade |
| Apr 2, 1990 | Trade | Drew Hall | Texas Rangers | Montreal Expos | Trade |
| Apr 1, 1990 | Signed | Armando Benitez | — | Baltimore Orioles | Amateur free agent signing |
| Apr 1, 1990 | Trade | Terry Wells | Houston Astros | Los Angeles Dodgers | Trade |
| Apr 1, 1990 | Trade | Franklin Stubbs | Los Angeles Dodgers | Houston Astros | Trade |
| Mar 31, 1990 | Released | Mark Lee | Kansas City Royals | — | Release |
| Mar 31, 1990 | Released | Brett Merriman | Cleveland Indians | — | Release |
| Mar 31, 1990 | Released | Rich Sauveur | Pittsburgh Pirates | — | Release |
| Mar 31, 1990 | Trade | Jose de Jesus | Kansas City Royals | Philadelphia Phillies | Trade |
| Mar 31, 1990 | Trade | Steve Jeltz | Philadelphia Phillies | Kansas City Royals | Trade |
| Mar 30, 1990 | Released | Jeff Gray | Philadelphia Phillies | — | Release |
| Mar 30, 1990 | Released | Tracy Woodson | Chicago White Sox | — | Release |
| Mar 30, 1990 | Trade | Doug Strange | Detroit Tigers | Houston Astros | Trade |
| Mar 30, 1990 | Trade | Lou Frazier | Houston Astros | Detroit Tigers | Trade |
| Mar 27, 1990 | Released | Andy Allanson | Cleveland Indians | — | Release |
| Mar 26, 1990 | Signed | D. J. Dozier | — | New York Mets | Amateur free agent signing |
| Mar 26, 1990 | Signed | Julian Tavarez | — | Cleveland Indians | Amateur free agent signing |
| Mar 18, 1990 | Trade | Tommy Hinzo | Cleveland Indians | Atlanta Braves | Trade |
| Mar 18, 1990 | Trade | Jeff Wetherby | Atlanta Braves | Cleveland Indians | Trade |
| Mar 18, 1990 | Trade | Miguel Sabino | Atlanta Braves | Cleveland Indians | Trade |
| Mar 17, 1990 | Signed as free agent | Eric Bullock | — | Montreal Expos | Free agent signing |
| Mar 13, 1990 | Signed as free agent | Ed Vosberg | — | San Francisco Giants | Free agent signing |
| Mar 13, 1990 | Trade | Orlando Miller | New York Yankees | Houston Astros | Trade |
| Mar 13, 1990 | Trade | Dave Silvestri | Houston Astros | New York Yankees | Trade |
| Mar 7, 1990 | Signed as free agent | Mark Huismann | — | Pittsburgh Pirates | Free agent signing |
| Mar 7, 1990 | Signed | Dan Miceli | — | Kansas City Royals | Amateur free agent signing |
| Mar 5, 1990 | Released | Robinson Checo | California Angels | — | Release |
| Mar 2, 1990 | Signed as free agent | Chris Bushing | — | Montreal Expos | Free agent signing |
| Mar 1990 | Signed as free agent | Jerry Reuss | — | Chicago White Sox | Free agent signing |
| Feb 28, 1990 | Signed as free agent | John Candelaria | — | Minnesota Twins | Free agent signing |
| Feb 28, 1990 | Signed | Wilson Heredia | — | Texas Rangers | Amateur free agent signing |
| Feb 27, 1990 | Trade | Alex Cole | St. Louis Cardinals | San Diego Padres | Trade |
| Feb 27, 1990 | Trade | Steve Peters | St. Louis Cardinals | San Diego Padres | Trade |
| Feb 27, 1990 | Trade | Omar Olivares | San Diego Padres | St. Louis Cardinals | Trade |
| Feb 27, 1990 | Trade | Pat Pacillo | Montreal Expos | Seattle Mariners | Trade |
| Feb 27, 1990 | Trade | Jerry Goff | Seattle Mariners | Montreal Expos | Trade |
| Feb 22, 1990 | Signed as free agent | Danny Boone | — | Baltimore Orioles | Free agent signing |
| Feb 21, 1990 | Signed as free agent | Greg Minton | — | California Angels | Free agent signing |
| Feb 20, 1990 | Signed as free agent | Don Aase | — | Los Angeles Dodgers | Free agent signing |
| Feb 20, 1990 | Signed as free agent | Sam Horn | — | Baltimore Orioles | Free agent signing |
| Feb 20, 1990 | Signed | Felipe Lira | — | Detroit Tigers | Amateur free agent signing |
| Feb 20, 1990 | Signed as free agent | Al Nipper | — | Cleveland Indians | Free agent signing |
| Feb 18, 1990 | Signed | Julio Santana | — | Texas Rangers | Amateur free agent signing |
| Feb 17, 1990 | Signed | Mariano Rivera | — | New York Yankees | Amateur free agent signing |
| Feb 16, 1990 | Signed as free agent | Dave Collins | — | St. Louis Cardinals | Free agent signing |
| Feb 16, 1990 | Signed as free agent | Israel Sanchez | — | Kansas City Royals | Free agent signing |
| Feb 15, 1990 | Signed as free agent | Bill Buckner | — | Boston Red Sox | Free agent signing |
| Feb 15, 1990 | Signed | Eddy Diaz | — | Seattle Mariners | Amateur free agent signing |
| Feb 15, 1990 | Signed as free agent | Greg Harris | — | Boston Red Sox | Free agent signing |
| Feb 15, 1990 | Signed as free agent | Pat Sheridan | — | Kansas City Royals | Free agent signing |
| Feb 15, 1990 | Signed as free agent | Reggie Williams | — | California Angels | Free agent signing |
| Feb 13, 1990 | Signed | Roberto Petagine | — | Houston Astros | Amateur free agent signing |
| Feb 12, 1990 | Signed as free agent | Jim Olander | — | Houston Astros | Free agent signing |
| Feb 10, 1990 | Signed | Roberto Duran | — | Los Angeles Dodgers | Amateur free agent signing |
| Feb 10, 1990 | Signed | Willis Otanez | — | Los Angeles Dodgers | Amateur free agent signing |
| Feb 6, 1990 | Signed as free agent | Mike Dalton | — | Boston Red Sox | Free agent signing |
| Feb 5, 1990 | Signed as free agent | Jim Pankovits | — | Boston Red Sox | Free agent signing |
| Feb 5, 1990 | Signed as free agent | Rick Schu | — | California Angels | Free agent signing |
| Feb 3, 1990 | Released | Greg Minton | California Angels | — | Release |
| Feb 2, 1990 | Signed as free agent | Mark Clear | — | California Angels | Free agent signing |
| Feb 2, 1990 | Signed | Nerio Rodriguez | — | Chicago White Sox | Amateur free agent signing |
| Feb 2, 1990 | Signed as free agent | Ozzie Virgil | — | Toronto Blue Jays | Free agent signing |
| Feb 1, 1990 | Signed as free agent | Brian Fisher | — | Houston Astros | Free agent signing |
| Feb 1, 1990 | Signed as free agent | Mark Thurmond | — | Houston Astros | Free agent signing |
| Jan 31, 1990 | Signed as free agent | Wally Backman | — | Pittsburgh Pirates | Free agent signing |
| Jan 30, 1990 | Signed as free agent | Dann Bilardello | — | Pittsburgh Pirates | Free agent signing |
| Jan 29, 1990 | Signed as free agent | Skeeter Barnes | — | Cincinnati Reds | Free agent signing |
| Jan 29, 1990 | Signed as free agent | Jim Eppard | — | Toronto Blue Jays | Free agent signing |
| Jan 28, 1990 | Signed as free agent | Dan Quisenberry | — | San Francisco Giants | Free agent signing |
| Jan 26, 1990 | Signed as free agent | Terry Clark | — | Houston Astros | Free agent signing |
| Jan 26, 1990 | Signed as free agent | Pat Perry | — | Los Angeles Dodgers | Free agent signing |
| Jan 25, 1990 | Signed | Luis Andujar | — | Chicago White Sox | Amateur free agent signing |
| Jan 24, 1990 | Released | John Candelaria | Montreal Expos | — | Release |
| Jan 24, 1990 | Trade | Jim Presley | Seattle Mariners | Atlanta Braves | Trade |
| Jan 24, 1990 | Trade | Gary Eave | Atlanta Braves | Seattle Mariners | Trade |
| Jan 24, 1990 | Trade | Ken Pennington | Atlanta Braves | Seattle Mariners | Trade |
| Jan 23, 1990 | Signed | Giovanni Carrara | — | Toronto Blue Jays | Amateur free agent signing |
| Jan 23, 1990 | Signed as free agent | Matt Stark | — | Chicago White Sox | Free agent signing |
| Jan 22, 1990 | Signed as free agent | Dan Petry | — | Detroit Tigers | Free agent signing |
| Jan 22, 1990 | Signed as free agent | Kevin Ward | — | Oakland Athletics | Free agent signing |
| Jan 20, 1990 | Signed as free agent | Joe Kmak | — | Milwaukee Brewers | Free agent signing |
| Jan 20, 1990 | Signed as free agent | Randy O'Neal | — | San Francisco Giants | Free agent signing |
| Jan 19, 1990 | Signed as free agent | Gary Carter | — | San Francisco Giants | Free agent signing |
| Jan 16, 1990 | Signed as free agent | Dave Leiper | — | Oakland Athletics | Free agent signing |
| Jan 15, 1990 | Signed | Fausto Cruz | — | Oakland Athletics | Amateur free agent signing |
| Jan 15, 1990 | Signed as free agent | Cecil Fielder | — | Detroit Tigers | Free agent signing |
| Jan 15, 1990 | Signed as free agent | Ed Romero | — | Detroit Tigers | Free agent signing |
| Jan 15, 1990 | Signed as free agent | Mark Ryal | — | Pittsburgh Pirates | Free agent signing |
| Jan 14, 1990 | Signed as free agent | Mark Ross | — | Pittsburgh Pirates | Free agent signing |
| Jan 12, 1990 | Signed as free agent | Joe Price | — | Baltimore Orioles | Free agent signing |
| Jan 12, 1990 | Trade | Jim Davins | Minnesota Twins | Montreal Expos | Trade |
| Jan 12, 1990 | Trade | Jim Dwyer | Montreal Expos | Minnesota Twins | Trade |
| Jan 11, 1990 | Signed as free agent | Ronn Reynolds | — | San Diego Padres | Free agent signing |
| Jan 10, 1990 | Signed | Tilson Brito | — | Toronto Blue Jays | Amateur free agent signing |
| Jan 10, 1990 | Signed | Raul Chavez | — | Houston Astros | Amateur free agent signing |
| Jan 10, 1990 | Signed | Jose Herrera | — | Toronto Blue Jays | Amateur free agent signing |
| Jan 10, 1990 | Signed | Sandy Martinez | — | Toronto Blue Jays | Amateur free agent signing |
| Jan 10, 1990 | Signed as free agent | Rafael Santana | — | Cleveland Indians | Free agent signing |
| Jan 10, 1990 | Trade | Mike Brumley | Detroit Tigers | Baltimore Orioles | Trade |
| Jan 10, 1990 | Trade | Larry Sheets | Baltimore Orioles | Detroit Tigers | Trade |
| Jan 9, 1990 | Signed as free agent | Nick Capra | — | Texas Rangers | Free agent signing |
| Jan 9, 1990 | Signed as free agent | Butch Davis | — | Los Angeles Dodgers | Free agent signing |
| Jan 9, 1990 | Signed as free agent | Efrain Valdez | — | Cleveland Indians | Free agent signing |
| Jan 9, 1990 | Trade | Scott Bailes | Cleveland Indians | California Angels | Trade |
| Jan 9, 1990 | Trade | Jeff Manto | California Angels | Cleveland Indians | Trade |
| Jan 9, 1990 | Trade | Colin Charland | California Angels | Cleveland Indians | Trade |
| Jan 8, 1990 | Signed as free agent | Carmelo Castillo | — | Minnesota Twins | Free agent signing |
| Jan 8, 1990 | Signed as free agent | Darrell Evans | — | Atlanta Braves | Free agent signing |
| Jan 5, 1990 | Signed | Fernando Hernandez | — | Cleveland Indians | Amateur free agent signing |
| Jan 5, 1990 | Signed as free agent | Donnie Hill | — | California Angels | Free agent signing |
| Jan 5, 1990 | Signed as free agent | Craig McMurtry | — | Texas Rangers | Free agent signing |
| Jan 5, 1990 | Signed as free agent | Paul Noce | — | Cincinnati Reds | Free agent signing |
| Jan 5, 1990 | Trade | Nikco Riesgo | San Diego Padres | New York Mets | Trade |
| Jan 5, 1990 | Trade | Craig Repoz | New York Mets | San Diego Padres | Trade |
| Jan 4, 1990 | Released | Chris Bushing | New York Yankees | — | Release |
| Jan 3, 1990 | Released | Jeff Bronkey | Minnesota Twins | — | Release |
| Jan 3, 1990 | Trade | Rey Sanchez | Texas Rangers | Chicago Cubs | Trade |
| Jan 3, 1990 | Trade | Bryan House | Chicago Cubs | Texas Rangers | Trade |
| Jan 2, 1990 | Released | Vance Law | Chicago Cubs | — | Release |
| Jan 2, 1990 | Signed as free agent | Mike Raczka | — | San Diego Padres | Free agent signing |
| Jan 1990 | Signed as free agent | Jay Baller | — | Kansas City Royals | Free agent signing |
| before the 1990 season | Signed as free agent | Rick Leach | — | Atlanta Braves | Free agent signing |
| before the 1990 season | Released | Rob Woodward | Boston Red Sox | — | Release |
| before the 1990 season | Signed as free agent | Rob Woodward | — | Baltimore Orioles | Free agent signing |
Every row is mapped onto the same trade / signing / release vocabulary the modern feed uses, with the era’s own type description kept on each row. Club names are the names of the day (the Boston Braves years, the Brooklyn Dodgers years), and each links to the franchise it is today. Some dates are only partially known or flagged approximate by the source; they are shown exactly as published, never completed to a fake precise day.