Junior Following his performance in minor hockey, the Colts selected Blackwood in the fifth round of the
2012 OHL Priority Selection. He earned his first
shutout on November 1, stopping all 31
shots from the
Niagara IceDogs. After leading all rookies in both the OHL and the
Canadian Hockey League (CHL) with a 2.98 GAA and .902
save percentage (SV%) and leading OHL rookies with 23 wins, Blackwood was named to the OHL First All-Rookie Team in 2014. Although the Colts' OHL postseason run came to an end with a loss to the
North Bay Battalion in the second playoff round, Blackwood was praised by coaches for his performance during the season, and he was expected to remain Barrie's starting goaltender for the remainder of his junior hockey career. The following season, Blackwood was selected to the OHL All-Stars for the 2014
Subway Super Series. He was also chosen to play the
2015 CHL/NHL Top Prospects Game, but was unavailable due to illness.
Professional New Jersey Devils On December 30, 2015, Blackwood signed a three-year, entry-level contract with the
New Jersey Devils, who had drafted him in the
2015 NHL entry draft. After playing for the Devils'
American Hockey League (AHL) affiliate, Blackwood was assigned to the
Adirondack Thunder, the Devils'
ECHL affiliate, on January 1, 2018. Blackwood began the
2018–19 season with the Devils' AHL affiliate, the
Binghamton Devils. He was recalled to New Jersey on December 17 after goaltender
Cory Schneider was placed on injured reserve. Blackwood made his NHL debut the following night in a 7–2 loss to the
Toronto Maple Leafs. He replaced starter
Keith Kinkaid in the third period and saved eight of 10 shots. On December 20, Blackwood made his first NHL start against the
Columbus Blue Jackets, and although the Devils lost 2–1, Blackwood had an impressive performance, saving 36 of 38 shots. On December 27, Blackwood recorded his first NHL win, a 5–2 victory over the
Boston Bruins, with another strong performance, making 40 saves on 42 shots. In his third NHL start, Blackwood recorded 37 saves to earn his first shutout in a 2–0 victory over the
Carolina Hurricanes on December 29. Blackwood was named a
Star of the Week following this performance. Following another shutout victory on December 31 against the
Vancouver Canucks, Blackwood became the first Devils rookie goaltender to post back-to-back shutouts. He also became the youngest Devils goaltender to record multiple regular season shutouts, surpassing
Martin Brodeur. On January 3, 2019, Blackwood was named to the North Division roster for the 2019 AHL All-Star Classic. On January 10, Blackwood was placed on injured reserve by the Devils due to a lower-body injury he suffered on January 2. He returned to the Devils and played his first game since January 4 in a 3–2 win over the
Philadelphia Flyers on January 12. during a game in January 2022 On December 23, 2020, the Devils re-signed Blackwood to a three-year contract.
San Jose Sharks As a pending restricted free agent with the Devils, Blackwood was traded to the San Jose Sharks for a
2023 sixth-round pick on June 27, 2023. On July 1, he signed a two-year deal with the Sharks. His debut for the Sharks came in the early stages of the
2023–24 season on October 14, in a 2–1 shootout loss to the
Colorado Avalanche, in which he made 51 saves.
Colorado Avalanche, Jennings Trophy On December 9, 2024, Blackwood was traded by the Sharks to the Colorado Avalanche, along with
Givani Smith and a fifth-round pick in the 2027 NHL entry draft, for
Alexandar Georgiev,
Nikolai Kovalenko, a
2025 conditional fifth-round pick, and a second-round pick in the
2026 NHL entry draft. Blackwood made his debut with the Avalanche on December 14, registering 37 saves in a 5–2 victory over the
Nashville Predators. After four outings with Colorado, Blackwood agreed to a five-year, $26.25 million contract extension to remain with the Avalanche through 2030 on December 27, 2024. With the Avalanche completely revamping the goaltender position during the season, with former Devils teammate
Scott Wedgewood having earlier been acquired to serve as backup, Blackwood helped stabilize the net and was a central reason for improved defensive play in the backend. He recorded his first shutout for the Avalanche in a 5–0 victory over the
St. Louis Blues on January 31, 2025. Among the top statistical goaltenders from the time he joined the Avalanche, Blackwood completed the regular season making 37 regular-season appearances with Colorado. In those appearances, he started 36 times and notched 22 wins along with a .913 save percentage, a 2.33 goals-against average, and 3 shutouts. Blackwood joined
Darcy Kuemper as the only goaltenders in franchise history to post at least 22 wins and three shutouts in their first 37 appearances with the team. Making his NHL post-season debut on April 20, 2025, Blackwood posted a victory in
Game 1 against divisional rivals the
Dallas Stars. He posted his first career playoff shutout, making 23 saves, in a Game 4 4–0 victory on April 27, 2025. Blackwood notched 3 wins and posted a 2.71 goal against average in the series before the Avalanche lost the series. Blackwood started the
2025–26 season out of the lineup, rehabbing from an off-season surgery to fix a lower-body injury. He made his first start of the season against his former team, the Sharks, on November 1, losing in overtime. He earned his first win of the season, a 5–4 overtime decision, eight days later against the Vancouver Canucks. At the conclusion of the regular season, Blackwood and teammate
Scott Wedgewood won the
William M. Jennings Trophy after giving up the fewest goals against, at 197. The last member of the Avalanche to win the trophy was
Patrick Roy in the
2001-2002 NHL season. Blackwood finished the season 8th in goals against average and 20th in save percentage. ==International play==