Cubs Roster & Staff
Transactions
| Date | Transaction |
| 05/31/21 | Chicago Cubs recalled RHP Kohl Stewart from Iowa Cubs. |
| 05/31/21 | Chicago Cubs placed RHP Trevor Williams on the 10-day injured list. Appendicitis. |
| 05/31/21 | Chicago Cubs released RHP Shelby Miller. |
| 05/30/21 | Chicago Cubs designated RHP Tyson Miller for assignment. |
| 05/30/21 | Chicago Cubs placed 2B David Bote on the 10-day injured list. Dislocated left shoulder. |
| 05/30/21 | Chicago Cubs selected the contract of SS Sergio Alcantara from Iowa Cubs. |
| 05/29/21 | Chicago Cubs signed free agent 2B Dee Strange-Gordon to a minor league contract. |
| 05/28/21 | Chicago Cubs signed free agent 2B Tyler Ladendorf to a minor league contract. |
| 05/26/21 | Chicago Cubs sent RHP Trevor Megill on a rehab assignment to Iowa Cubs. |
| 05/26/21 | Chicago Cubs placed 2B Nico Hoerner on the 10-day injured list. Left hamstring strain. |
| 05/26/21 | Chicago Cubs activated RHP Shelby Miller. |
| 05/26/21 | Chicago Cubs selected the contract of LF Rafael Ortega, , and from Iowa Cubs. |
| 05/26/21 | Chicago Cubs designated RHP Shelby Miller for assignment. |
| 05/26/21 | Chicago Cubs released RHP Jason Adam. |
| 05/25/21 | Chicago Cubs placed 3B Matt Duffy on the 10-day injured list. Low back strain. |
| 05/25/21 | Chicago Cubs designated RHP Jason Adam for assignment. |
| 05/25/21 | Chicago Cubs selected the contract of 3B Patrick Wisdom from Iowa Cubs. |
| 05/23/21 | Chicago Cubs sent RHP Alec Mills on a rehab assignment to Iowa Cubs. |
| 05/22/21 | Chicago Cubs signed free agent Jarod Wright to a minor league contract. |
| 05/22/21 | Chicago Cubs sent C Tony Wolters outright to Iowa Cubs. |
| 05/21/21 | Chicago Cubs placed LHP Justin Steele on the 10-day injured list. Right hamstring strain. |
| 05/21/21 | Chicago Cubs recalled LHP Brad Wieck from Iowa Cubs. |
| 05/20/21 | Chicago Cubs recalled LF Nick Martini. |
| 05/20/21 | Chicago Cubs recalled LF Nick Martini from Iowa Cubs. |
| 05/20/21 | Chicago Cubs recalled LF Nick Martini. |
| 05/20/21 | Chicago Cubs placed RF Jason Heyward on the 10-day injured list. Left hamstring strain. |
| 05/19/21 | Chicago Cubs designated C Tony Wolters for assignment. |
| 05/19/21 | Chicago Cubs selected the contract of C P.J. Higgins from Iowa Cubs. |
| 05/18/21 | Chicago Cubs signed free agent OF Raul Guzman to a minor league contract. |
| 05/18/21 | Chicago Cubs signed free agent RHP Starlyn Pichardo to a minor league contract. |
| 05/18/21 | Chicago Cubs signed free agent RHP Tomy Sanchez to a minor league contract. |
| 05/18/21 | Chicago Cubs traded CF Cameron Maybin to New York Mets for cash. |
| 05/18/21 | Chicago Cubs signed free agent LHP Carlos Garcia to a minor league contract. |
| 05/17/21 | Pittsburgh Pirates claimed 2B Ildemaro Vargas off waivers from Chicago Cubs. |
| 05/16/21 | Chicago Cubs placed RHP Alec Mills on the 10-day injured list. Lower back strain. |
| 05/16/21 | Chicago Cubs selected the contract of RHP Tommy Nance from Iowa Cubs. |
| 05/15/21 | Chicago Cubs designated 2B Ildemaro Vargas for assignment. |
| 05/15/21 | Chicago Cubs activated CF Ian Happ from the 10-day injured list. |
| 05/14/21 | Chicago Cubs activated RHP Jake Arrieta from the 10-day injured list. |
| 05/14/21 | Chicago Cubs signed RHP Tyler Suellentrop. |
| 05/14/21 | Chicago Cubs optioned LF Nick Martini to Iowa Cubs. |
| 05/14/21 | Chicago Cubs activated RHP Dan Winkler from the 10-day injured list. |
| 05/14/21 | Chicago Cubs optioned RHP Jason Adam to Iowa Cubs. |
| 05/14/21 | Chicago Cubs activated 2B Nico Hoerner from the 10-day injured list. |
| 05/14/21 | Chicago Cubs optioned LHP Brad Wieck to Iowa Cubs. |
| 05/11/21 | Chicago Cubs sent LHP Kyle Ryan outright to Iowa Cubs. |
| 05/11/21 | Chicago Cubs recalled LHP Brad Wieck from Iowa Cubs. |
| 05/11/21 | Arizona Diamondbacks traded RF Trayce Thompson to Chicago Cubs. |
| 05/11/21 | Chicago Cubs placed CF Jake Marisnick on the 10-day injured list. Right hamstring strain. |
| 05/10/21 | Chicago Cubs signed free agent RHP Adrian Sampson to a minor league contract. |
| 05/09/21 | Chicago Cubs sent RHP Shelby Miller on a rehab assignment to Iowa Cubs. |
| 05/07/21 | Chicago Cubs designated LHP Kyle Ryan for assignment. |
| 05/07/21 | Chicago Cubs recalled RHP Jason Adam from Iowa Cubs. |
| 05/07/21 | Chicago Cubs selected the contract of LF Nick Martini from Iowa Cubs. |
| 05/07/21 | Chicago Cubs placed CF Ian Happ on the 10-day injured list. Left rib contusion. |
| 05/05/21 | Chicago Cubs optioned RHP Tyson Miller to Iowa Cubs. |
| 05/05/21 | Chicago Cubs optioned RHP Kohl Stewart to Iowa Cubs. |
| 05/05/21 | Chicago Cubs placed C Austin Romine on the 60-day injured list. |
| 05/04/21 | Chicago Cubs placed RHP Jake Arrieta on the 10-day injured list. Right thumb abrasion. |
| 05/04/21 | Chicago Cubs selected the contract of 2B Ildemaro Vargas from Iowa Cubs. |
| 05/04/21 | Chicago Cubs recalled RHP Kohl Stewart from Iowa Cubs. |
| 05/04/21 | Chicago Cubs recalled RHP Keegan Thompson from Cubs Alternate Training Site. |
| 05/04/21 | Chicago Cubs signed free agent LHP Alex Katz to a minor league contract. |
| 05/04/21 | Chicago Cubs signed free agent RHP Austin Krzeminski to a minor league contract. |
| 05/03/21 | Chicago Cubs activated CF Joc Pederson from the 10-day injured list. |
| 05/03/21 | Chicago Cubs placed SS Nico Hoerner on the 10-day injured list. Left forearm strain. |
| 05/03/21 | Chicago Cubs placed RHP Dan Winkler on the 10-day injured list. Right triceps tendinitis. |
| 05/03/21 | Chicago Cubs signed free agent LHP Ryan Kellogg to a minor league contract. |
| 05/03/21 | Chicago Cubs optioned RHP Keegan Thompson to Cubs Alternate Training Site. |
| 05/03/21 | Chicago Cubs recalled LHP Kyle Ryan from Iowa Cubs. |
| 05/01/21 | Chicago Cubs optioned LHP Kyle Ryan to Iowa Cubs. |
| 05/01/21 | Chicago Cubs recalled RHP Keegan Thompson from Iowa Cubs. |