| Transactions |
| Date | Team | Player | Type | OthTm | EffDate | When |
| 2/24/2021 | ACS | Brujan | Traded away | VD | | After |
| 2/24/2021 | ACS | Giolito | Acquired via trade | VD | | After |
| 2/24/2021 | ACS | Valdez,F | Traded away | VD | | After |
| 3/25/2021 | SFR | Bauer | Traded away | VD | | After |
| 3/25/2021 | SFR | LeMahieu | Acquired via trade | VD | | After |
| 3/25/2021 | SFR | Lodolo | Acquired via trade | VD | | After |
| 3/25/2021 | SFR | McCullers | Traded away | VD | | After |
| 3/25/2021 | SFR | Soler | Acquired via trade | VD | | After |
| 4/8/2021 | ACS | Jackson,L | Demoted to reserve roster | | | Before |
| 4/8/2021 | BC | Mahle | Demoted to reserve roster | | | Before |
| 4/8/2021 | BC | Urquidy | Demoted to reserve roster | | | Before |
| 4/8/2021 | PL | Marte,N | Demoted to reserve roster | | | Before |
| 4/8/2021 | SFR | Kelenic | Demoted to reserve roster | | | Before |
| 4/8/2021 | WN | Lindor | Demoted to reserve roster | | | Before |
| 4/8/2021 | WN | Walker,T | Demoted to reserve roster | | | Before |
| 4/10/2021 | BTB | Hayes | Promoted to active roster | | | Before |
| 4/10/2021 | BTB | Howard,Sp | Demoted to reserve roster | | | Before |
| 4/10/2021 | BTB | Stammen | Signed | | | Before |
| 4/12/2021 | AH | Contreras,R | Demoted to reserve roster | | | Before |
| 4/13/2021 | PL | Hernandez,Ca | Demoted to reserve roster | | | Before |
| 4/13/2021 | PL | McClanahan | Promoted to active roster | | | Before |
| 4/15/2021 | ACS | Cabrera,G | Demoted to reserve roster | | | Before |
| 4/15/2021 | AH | Sanchez,G | Signed | | | Before |
| 4/17/2021 | BTB | Fulmer,M | Promoted to active roster | | | Before |
| 4/17/2021 | BTB | Heuer | Demoted to reserve roster | | | Before |
| 4/17/2021 | PL | Hernandez,Ca | Promoted to active roster | | | Before |
| 4/17/2021 | PL | Matz | Demoted to reserve roster | | | Before |
| 4/18/2021 | ACS | Jackson,L | Promoted to active roster | | | Before |
| 4/19/2021 | PL | Baddoo | Promoted to active roster | | | Before |
| 4/21/2021 | ACS | Longoria | Acquired via trade | AH | | After |
| 4/21/2021 | ACS | Luzardo | Traded away | AH | | After |
| 4/21/2021 | AH | Longoria | Traded away | ACS | | After |
| 4/21/2021 | AH | Luzardo | Acquired via trade | ACS | | After |
| 4/22/2021 | ACS | Zimmerman | Demoted to reserve roster | | | Before |
| 4/24/2021 | PL | Hernandez,Ca | Demoted to reserve roster | | | Before |
| 4/24/2021 | PL | Montgomery | Promoted to active roster | | | Before |
| 4/24/2021 | PL | Betts | Traded away | HS | | After |
| 4/24/2021 | PL | Haase | Acquired via trade | HS | | After |
| 4/24/2021 | PL | Torkelson | Acquired via trade | HS | | After |
| 4/24/2021 | PL | VanMeter | Acquired via trade | HS | | After |
| 4/25/2021 | AH | Chisholm | Traded away | BTB | | After |
| 4/25/2021 | AH | Hayes | Acquired via trade | BTB | | After |
| 4/25/2021 | BTB | Chisholm | Acquired via trade | AH | | After |
| 4/25/2021 | BTB | Hayes | Traded away | AH | | After |
| 4/25/2021 | PL | Molina | Demoted to reserve roster | | | Before |
| 4/26/2021 | AH | Torres | Demoted to reserve roster | | | Before |
| 4/28/2021 | PL | Eflin | Demoted to reserve roster | | | Before |
| 4/28/2021 | PL | Hernandez,Ca | Promoted to active roster | | | Before |
| 4/30/2021 | AH | Frazier,A | Traded away | End | | After |
| 4/30/2021 | AH | Rizzo | Acquired via trade | End | | After |
| 4/30/2021 | AH | Wisdom | Traded away | End | | After |
| 5/2/2021 | ACS | Beer | Traded away | PL | | After |
| 5/2/2021 | ACS | Nimmo | Traded away | PL | | After |
| 5/2/2021 | ACS | Pache | Traded away | PL | | After |
| 5/2/2021 | ACS | Pollock | Acquired via trade | PL | | After |
| 5/2/2021 | AH | Duffy,D | Traded away | PL | | After |
| 5/2/2021 | AH | Martin,A | Traded away | PL | | After |
| 5/2/2021 | PL | Beer | Acquired via trade | ACS | | After |
| 5/2/2021 | PL | Duffy,D | Acquired via trade | AH | | After |
| 5/2/2021 | PL | Martin,A | Acquired via trade | AH | | After |
| 5/2/2021 | PL | Nimmo | Acquired via trade | ACS | | After |
| 5/2/2021 | PL | Pache | Acquired via trade | ACS | | After |
| 5/2/2021 | PL | Pollock | Traded away | ACS | | After |
| 5/4/2021 | PL | Hernandez,Ca | Demoted to reserve roster | | | Before |
| 5/10/2021 | ACS | Crochet | Demoted to reserve roster | | | Before |
| 5/13/2021 | BTB | Canha | Acquired via trade | WN | | After |
| 5/13/2021 | BTB | Means | Traded away | WN | | After |
| 5/13/2021 | WN | Canha | Traded away | BTB | | After |
| 5/13/2021 | WN | Means | Acquired via trade | BTB | | After |
| 5/14/2021 | BTB | Abreu,J | Demoted to reserve roster | | | Before |
| 5/14/2021 | BTB | Canha | Promoted to active roster | | | Before |
| 5/14/2021 | BTB | Hendricks | Promoted to active roster | | | Before |
| 5/15/2021 | ACS | Hoskins | Traded away | BB | | After |
| 5/15/2021 | ACS | Reyes,F | Acquired via trade | BB | | After |
| 5/19/2021 | BTB | Abreu,J | Promoted to active roster | | | Before |
| 5/19/2021 | BTB | Canha | Demoted to reserve roster | | | Before |
| 5/20/2021 | ACS | Brantley | Traded away | VD | | After |
| 5/20/2021 | ACS | Clevenger | Acquired via trade | VD | | After |
| 5/20/2021 | ACS | Correa | Acquired via trade | VD | | After |
| 5/20/2021 | ACS | Diaz,Ed | Traded away | WN | | After |
| 5/20/2021 | ACS | Gausman | Traded away | WN | | After |
| 5/20/2021 | ACS | Houck | Traded away | VD | | After |
| 5/20/2021 | ACS | Lindor | Acquired via trade | WN | | After |
| 5/20/2021 | ACS | Longoria | Traded away | VD | | After |
| 5/20/2021 | ACS | Marsh | Acquired via trade | VD | | After |
| 5/20/2021 | ACS | Ross | Acquired via trade | WN | | After |
| 5/20/2021 | ACS | Treinen | Traded away | VD | | After |
| 5/20/2021 | ACS | Walker,T | Acquired via trade | WN | | After |
| 5/20/2021 | WN | Diaz,Ed | Acquired via trade | ACS | | After |
| 5/20/2021 | WN | Gausman | Acquired via trade | ACS | | After |
| 5/20/2021 | WN | Lindor | Traded away | ACS | | After |
| 5/20/2021 | WN | Ross | Traded away | ACS | | After |
| 5/20/2021 | WN | Walker,T | Traded away | ACS | | After |
| 5/21/2021 | ACS | Crochet | Promoted to active roster | | | Before |
| 5/21/2021 | ACS | Gray,Jon | Promoted to active roster | | | Before |
| 5/21/2021 | ACS | Lindor | Promoted to active roster | | | Before |
| 5/21/2021 | ACS | Walker,T | Promoted to active roster | | | Before |
| 5/21/2021 | WN | Kennedy | Demoted to reserve roster | | | Before |
| 5/22/2021 | AH | Hernandez,Ca | Acquired via trade | PL | | After |
| 5/22/2021 | AH | Kittredge | Traded away | PL | | After |
| 5/22/2021 | AH | Matz | Acquired via trade | PL | | After |
| 5/22/2021 | AH | Sulser | Traded away | PL | | After |
| 5/22/2021 | PL | Hernandez,Ca | Traded away | AH | | After |
| 5/22/2021 | PL | Kittredge | Acquired via trade | AH | | After |
| 5/22/2021 | PL | Matz | Traded away | AH | | After |
| 5/22/2021 | PL | Sulser | Acquired via trade | AH | | After |
| 5/23/2021 | AH | Hernandez,Ca | Promoted to active roster | | | Before |
| 5/23/2021 | AH | Matz | Promoted to active roster | | | Before |
| 5/23/2021 | PL | Barlow,S | Demoted to reserve roster | | | Before |
| 5/23/2021 | PL | Rogers,Ta | Demoted to reserve roster | | | Before |
| 6/2/2021 | PL | Barlow,S | Promoted to active roster | | | Before |
| 6/2/2021 | PL | White,M | Demoted to reserve roster | | | Before |
| 6/3/2021 | ACS | Cobb | Traded away | PL | | After |
| 6/3/2021 | PL | Cobb | Acquired via trade | ACS | | After |
| 6/4/2021 | ACS | Cabrera,G | Promoted to active roster | | | Before |
| 6/4/2021 | ACS | Cowser | Acquired via trade | VD | | After |
| 6/4/2021 | ACS | Culberson | Acquired via trade | VD | | After |
| 6/4/2021 | ACS | Ruf | Traded away | VD | | After |
| 6/4/2021 | PL | Montgomery | Demoted to reserve roster | | | Before |
| 6/28/2021 | PL | Barlow,S | Demoted to reserve roster | | | Before |
| 6/28/2021 | PL | Rogers,Ta | Promoted to active roster | | | Before |
| 6/28/2021 | PL | Sewald | Demoted to reserve roster | | | Before |
| 6/28/2021 | PL | White,M | Promoted to active roster | | | Before |
| 7/1/2021 | ACS | Cowser | Traded away | WN | | After |
| 7/1/2021 | ACS | Marsh | Traded away | WN | | After |
| 7/1/2021 | ACS | Rogers,Ty | Acquired via trade | WN | | After |
| 7/1/2021 | ACS | Wade,L | Acquired via trade | WN | | After |
| 7/1/2021 | WN | Cowser | Acquired via trade | ACS | | After |
| 7/1/2021 | WN | Marsh | Acquired via trade | ACS | | After |
| 7/1/2021 | WN | Rogers,Ty | Traded away | ACS | | After |
| 7/1/2021 | WN | Wade,L | Traded away | ACS | | After |
| 7/2/2021 | ACS | Culberson | Demoted to reserve roster | | | Before |
| 7/2/2021 | ACS | DeJong | Demoted to reserve roster | | | Before |
| 7/2/2021 | WN | Kennedy | Promoted to active roster | | | Before |
| 7/5/2021 | ACS | Arraez | Traded away | SFR | | After |
| 7/5/2021 | ACS | Belt | Acquired via trade | SFR | | After |
| 7/5/2021 | ACS | Clevenger | Traded away | WN | | After |
| 7/5/2021 | ACS | Jones,AJ | Traded away | WN | | After |
| 7/5/2021 | ACS | Posey | Acquired via trade | WN | | After |
| 7/5/2021 | ACS | Wells,T | Acquired via trade | WN | | After |
| 7/5/2021 | SFR | Arraez | Acquired via trade | ACS | | After |
| 7/5/2021 | SFR | Belt | Traded away | ACS | | After |
| 7/5/2021 | WN | Clevenger | Acquired via trade | ACS | | After |
| 7/5/2021 | WN | Jones,AJ | Acquired via trade | ACS | | After |
| 7/5/2021 | WN | Posey | Traded away | ACS | | After |
| 7/5/2021 | WN | Wells,T | Traded away | ACS | | After |
| 7/6/2021 | ACS | Cabrera,G | Demoted to reserve roster | | | Before |
| 7/6/2021 | WN | Marsh | Promoted to active roster | | | Before |
| 7/8/2021 | PL | Bell | Traded away | BB | | After |
| 7/8/2021 | PL | Hoskins | Acquired via trade | BB | | After |
| 7/12/2021 | WN | Garver | Traded away | VD | | After |
| 7/12/2021 | WN | Stallings | Acquired via trade | VD | | After |
| 7/13/2021 | PL | Crawford,B | Traded away | HS | | After |
| 7/13/2021 | PL | Freeman,F | Traded away | End | | After |
| 7/13/2021 | PL | Lowe,B | Traded away | End | | After |
| 7/13/2021 | PL | Lux | Acquired via trade | HS | | After |
| 7/13/2021 | PL | Melendez | Acquired via trade | HS | | After |
| 7/13/2021 | PL | Tucker,K | Acquired via trade | End | | After |
| 7/14/2021 | PL | Montgomery | Promoted to active roster | | | Before |
| 7/14/2021 | PL | Sewald | Promoted to active roster | | | Before |
| 7/14/2021 | PL | White,M | Demoted to reserve roster | | | Before |
| 7/16/2021 | ACS | Correa | Traded away | PL | | After |
| 7/16/2021 | ACS | Donaldson | Acquired via trade | PL | | After |
| 7/16/2021 | ACS | Eovaldi | Acquired via trade | PL | | After |
| 7/16/2021 | ACS | Moncada | Acquired via trade | PL | | After |
| 7/16/2021 | ACS | Story | Acquired via trade | PL | | After |
| 7/16/2021 | PL | Correa | Acquired via trade | ACS | | After |
| 7/16/2021 | PL | Donaldson | Traded away | ACS | | After |
| 7/16/2021 | PL | Eovaldi | Traded away | ACS | | After |
| 7/16/2021 | PL | Moncada | Traded away | ACS | | After |
| 7/16/2021 | PL | Story | Traded away | ACS | | After |
| 7/17/2021 | PL | Barlow,S | Promoted to active roster | | | Before |
| 7/18/2021 | ACS | Gray,S | Demoted to reserve roster | | | Before |
| 7/18/2021 | ACS | Solano | Demoted to reserve roster | | | Before |
| 7/18/2021 | ACS | Stassi | Demoted to reserve roster | | | Before |
| 7/21/2021 | PL | Eflin | Promoted to active roster | | | Before |
| 7/21/2021 | PL | Montgomery | Demoted to reserve roster | | | Before |
| 7/21/2021 | PL | Montgomery | Promoted to active roster | | | Before |
| 8/6/2021 | PL | Beer | Traded away | ShS | | After |
| 8/6/2021 | PL | Wendle | Acquired via trade | ShS | | After |
| 8/15/2021 | PL | Barlow,S | Demoted to reserve roster | | | Before |
| 8/15/2021 | PL | White,M | Promoted to active roster | | | Before |
| 8/17/2021 | PL | Haase | Demoted to reserve roster | | | Before |
| 8/17/2021 | PL | Molina | Promoted to active roster | | | Before |
| 9/19/2021 | ACS | Gray,S | Promoted to active roster | | | Before |
| 9/19/2021 | ACS | Walker,T | Demoted to reserve roster | | | Before |
| 10/3/2021 | PL | McClanahan | Traded away | HS | | After |
| 10/3/2021 | PL | Ruiz,K | Acquired via trade | HS | | After |
| 10/8/2021 | PL | Barlow,S | Promoted to active roster | | | Before |
| 10/8/2021 | PL | Haase | Promoted to active roster | | | Before |
| 10/8/2021 | PL | Sewald | Demoted to reserve roster | | | Before |