- DECEMBER 27: Ottawa Senators acquire forward Cedric Paquette, defenseman Braydon Coburn and a second-round pick in the 2022 NHL Draft from the Tampa Bay Lightning in exchange for goalie Anders Nilsson and forward Marian Gaborik.
- DECEMBER 26: Ottawa Senators acquire forward Derek Stepan from the Arizona Coyotes in exchange for a second-round pick in the 2021 NHL Draft.
- OCTOBER 12: Colorado Avalanche acquire defenseman Devon Toews from New York Islanders in exchange for 2021 second-round draft pick, 2022 second-round draft pick.
- OCTOBER 10: Ottawa Senators acquire forward Austin Watson from the Nashville Predators in exchange for 2021 fourth-round draft pick.
- OCTOBER 9: Winnipeg Jets acquire center Paul Stastny from the Vegas Golden Knights in exchange for defenseman Carl Dahlstrom, 2022 conditional fourth-round draft pick.
- OCTOBER 8: New Jersey Devils acquire defenseman Ryan Murray from the Columbus Blue Jackets in exchange for a 2021 fifth-round draft pick.
- OCTOBER 8: Ottawa Senators acquire defenseman Erik Gudbranson from Anaheim Ducks in exchange for 2021 fifth-round draft pick.
- OCTOBER 7: San Jose Sharks acquire 2020 second-round pick (No. 76) from Edmonton Oilers in exchange for 2020 fourth-round pick (No. 100), 2020 fifth-round pick (No. 126)
- OCTOBER 7: Montreal Canadiens acquire 2020 fourth-round pick (No. 124) and a 2021 second-round pick from the Tampa Bay Lightning in exchange for a 2020 second-round pick (No. 57)
- OCTOBER 7: Ottawa Senators acquire 2020 second-round Draft pick (No. 44) from the Toronto Maple Leafs in exchange for a 2020 second-round pick (No. 59) and a 2020 third-round pick (No. 64)
- OCTOBER 7: Detroit Red Wings acquire 2020 second-round Draft pick (No. 51) and 2020 fourth-round pick (No. 97) from the Los Angeles Kings in exchange for a 2020 second-round pick (No. 45)
- OCTOBER 7: Nashville Predators acquire forward Luke Kunin, 2020 draft pick (No. 101) from Minnesota Wild in exchange for forward Nick Bonino, 2020 draft picks (No. 37 and 70)
- OCTOBER 7: Ottawa Senators acquire goaltender Matt Murray from Pittsburgh Penguins in exchange for forward Jonathan Gruden, 2020 second-round pick (No. 52)
- OCTOBER 2: Ottawa Senators acquire defenseman Joshua Brown from Florida Panthers in exchange for 2020 fourth-round pick