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| 2021-09-17 18:40:00 | Dallas Hounds | Frank Kastner | Acquired via trade | Alfred Vail | Seattle Cougars |
| 2021-09-17 18:40:00 | Dallas Hounds | 1st round pick in season 32 | Acquired via trade | | Seattle Cougars |
| 2021-09-17 18:40:00 | Dallas Hounds | Donn Halley | Acquired via trade | | Seattle Cougars |
| 2021-09-17 18:40:00 | Dallas Hounds | Joel Morrison | Acquired via trade | | Seattle Cougars |
| 2021-09-17 18:38:00 | Indianapolis Tornadoes | Devin Vandal | Acquired via trade | Clinton Mitzel | Seattle Cougars |
| 2021-09-17 18:38:00 | Indianapolis Tornadoes | 3rd round pick in season 32 | Acquired via trade | | Seattle Cougars |
| 2021-09-17 16:33:56 | Seattle Cougars | | Demoted | Peyton Williams | Vancouver Mounties |
| 2021-09-17 16:33:28 | Seattle Cougars | Peyton Williams | Add/Drop | | |
| 2021-09-17 15:46:42 | Seattle Cougars | Kaleb Koss | Add/Drop | | |
| 2021-09-17 10:13:10 | Norfolk Wolves | | Promoted | Joel Morrison | Dallas Hounds |
| 2021-09-15 18:57:46 | San Antonio Brothas | | Drop | Garrett Park | |
| 2021-09-15 17:11:00 | New York Warriors | Lowell Nielsen | Add/Drop | | |
| 2021-09-15 15:16:10 | Seattle Cougars | | Demoted | Michael Nash | Vancouver Mounties |
| 2021-09-15 02:00:00 | San Antonio Brothas | Bailey Oakley | Acquired via trade | 2nd round pick in season 33 | Seattle Cougars |
| 2021-09-15 02:00:00 | San Antonio Brothas | 3rd round pick in season 33 | Acquired via trade | | Seattle Cougars |
| 2021-09-14 14:48:00 | Louisville Colonels | Rene Keller | Acquired via waivers | Francisco Tyner | Waiver |
| 2021-09-14 14:40:00 | Seattle Cougars | Donn Halley | Acquired via trade | 2nd round pick in season 32 | Atlanta Eels |
| 2021-09-14 14:40:00 | Seattle Cougars | 3rd round pick in season 32 | Acquired via trade | | Atlanta Eels |
| 2021-09-14 13:26:14 | Buffalo Bombers | | Promoted | Duane Briseno | Louisville Colonels |
| 2021-09-14 13:25:48 | Louisville Colonels | | Demoted | Rene Keller | Buffalo Bombers |
| 2021-09-14 00:52:14 | Atlanta Eels | Martin Solomon | Add/Drop | | |
| 2021-09-13 14:10:24 | Norfolk Wolves | | Promoted | German Thompson | Dallas Hounds |
| 2021-09-13 14:10:04 | Dallas Hounds | | Demoted | Michael Clapper | Norfolk Wolves |
| 2021-09-12 14:38:24 | South Dakota Blackhawks | | Promoted | Jason Taylor | Philadelphia Assassins |
| 2021-09-12 03:20:32 | Sao Paulo Jackalopes | | Promoted | Ali Batt | Cincinnati Skyliners |