| Transactions | ||||||
| Date | Team | Player | Type | OthTm | EffDate | When |
| 5/16/1990 | LON | Bordick | Released | Before | ||
| 5/28/1990 | ROK | Ward | Demoted to reserve roster | Before | ||
| 6/3/1990 | MAD | Vizquel | Promoted to active roster | Before | ||
| 6/8/1990 | GEO | Steinbach | Traded away | OTR | After | |
| 6/8/1990 | GEO | Stewart | Acquired via trade | OTR | After | |
| 6/8/1990 | OTR | Steinbach | Acquired via trade | GEO | After | |
| 6/8/1990 | OTR | Stewart | Traded away | GEO | After | |
| 6/15/1990 | GEO | Ojeda | Demoted to reserve roster | Before | ||
| 6/15/1990 | OTR | Steinbach | Promoted to active roster | Before | ||
| 7/8/1990 | LON | Martinez,Da | Acquired via trade | MAD | After | |
| 7/8/1990 | LON | Murray | Traded away | MAD | After | |
| 7/8/1990 | LON | Rojas | Acquired via trade | MAD | After | |
| 7/8/1990 | MAD | Martinez,Da | Traded away | LON | After | |
| 7/8/1990 | MAD | Murray | Acquired via trade | LON | After | |
| 7/8/1990 | MAD | Rojas | Traded away | LON | After | |
| 7/9/1990 | LON | Rojas | Demoted to reserve roster | Before | ||
| 7/26/1990 | ROK | Spiers | Acquired via trade | COP | After | |
| 7/26/1990 | ROK | Wilson | Traded away | COP | After | |
| 8/13/1990 | BON | Bell | Traded away | CRH | After | |
| 8/13/1990 | BON | Cangelosi | Traded away | CRH | After | |
| 8/13/1990 | BON | Maas | Acquired via trade | CRH | After | |
| 10/13/1990 | MAD | Boyd | Promoted to active roster | Before | ||
| 10/13/1990 | MAD | Terry | Demoted to reserve roster | Before | ||
| 10/20/1990 | BON | Fermin | Promoted to active roster | Before | ||