Amateur As a youth, Morrissey played in the 2007
Quebec International Pee-Wee Hockey Tournament with the Calgary Flames
minor ice hockey team. He was selected by the
Western Hockey League (WHL)'s
Prince Albert Raiders in the first round, sixth overall, of the 2010
WHL Bantam Draft after skating for Calgary Royals Gold, and being named the top bantam defenceman in southern Alberta. Morrissey made his WHL debut in 2010 skating in five games with Prince Albert, spending most of the season with the
Calgary Royals midget AAA team, and competing for Team Alberta during the 2011
Canada Winter Games in
Halifax, Nova Scotia. He helped lead Alberta to a bronze medal. In the
2012–13 season, Morrissey led Prince Albert defenceman in points, scoring 15 goals and 32 assists to go with a +14
plus-minus rating and 91 penalty minutes. The Raiders finished with a winning record for the first time since
2003–04. In the subsequent off-season, Morrissey was drafted by the
Winnipeg Jets in the first round, 13th overall, of the
2013 NHL entry draft. Prior to the beginning of the
2013–14 season, Morrissey was named captain of the Raiders. On October 3, 2013, the Winnipeg Jets signed him to three-year,
two-way contract, although he returned to Prince Albert for the season. He finished as the second-leading scorer in the WHL during the 2013–14 season, recording 28 goals and 45 assists (73 points) in 59 regular season games, along with a +6 plus-minus rating and 59 penalty minutes. The Raiders were fourth in the East Division before being swept by the eventual
2014 Memorial Cup champions, the
Edmonton Oil Kings, in the first round. On December 10, 2014, during the
2014–15 season, Morrissey was traded to the
Kelowna Rockets. He would help lead the Rockets to the WHL championship as well as to the final of the
2015 Memorial Cup, which they lost to the
Oshawa Generals.
Professional Morrissey was called up to Winnipeg's
American Hockey League (AHL) affiliate, the
St. John's IceCaps, during the
2013–14 season, playing eight regular season games as well as 20 games in the
2014 Calder Cup playoffs. The Jets assigned him to the
Manitoba Moose (their new AHL affiliate)
the following season, although they briefly called him up late in the season to make his NHL debut in a home game against the
Montreal Canadiens on March 5, 2016. Morrissey scored his first career NHL goal on November 15, 2016, in a 4–0 win over the
Chicago Blackhawks. He finished his first full season with the Jets with 6 goals and 20 points in 82 games. During his second season with the Jets, Morrissey recorded 26 points in 81 games to help the Jets qualify for the
2018 Stanley Cup playoffs. During the first round, Morrissey was suspended one game for cross-checking
Eric Staal of the
Minnesota Wild. On September 12, 2019, Morrissey signed an 8-year, $50 million extension with the Jets, carrying an annual average of $6.25 million. Later, on October 1, 2019, just before the start of the 2019–20 NHL season Morrissey was named an alternate captain of the Jets.
2025-26 Season Morrisey became the Jets' all-time leader in scoring by a defenceman following a March 7 game against the
Vancouver Canucks, passing
Dustin Byfuglien. ==International play==