Following the draft, Parayko played three seasons with the Alaska Nanooks, earning All-Western Collegiate Hockey Association (WCHA) First Team and West Second-Team All-American honors.[2] Growing up, Parayko spent his youth hockey career in his hometown of St. Albert, Alberta while attending Paul Kane High School.[6] At the conclusion of the 2009–10 season, he experienced a six-inch growth spurt and signed with the Fort McMurray Oil Barons of the Alberta Junior Hockey League (AJHL).[15] Parayko also received the Western Collegiate Hockey Association Defensive Player of the Year and was selected for their All-WCHA First Team alongside teammate Tyler Morley for the second time.[22] He earned praise from head coach Ken Hitchcock, who said "he's got poise with the puck and for a big man, he's got foot speed...He has great composure and he's getting better every day.[28] As a result of his dominating season, Parayko was selected for the NHL All-Rookie Team[25] and ranked eighth in Calder Memorial Trophy voting as rookie of the year.[31] During the offseason, Parayko competed in the 2016 World Cup of Hockey and graduated from the University of Alaska Fairbanks with a degree in Business Administration on August 12, 2016.[33] Picking up on the success of his previous season, Parayko tied the NHL's longest active point streak with five games and ranked fourth among all defensemen in assists by December.[5] Parayko began the 2018–19 season on a pairing with Jay Bouwmeester to lead the Blues' shutdown line, but would also play with Marco Scandella once he was acquired from the Montreal Canadiens.[42] He remained untraded after the deadline and helped lead the Blues to the 2019 Stanley Cup Finals against the Boston Bruins by recording two goals and 10 assists in 26 games during the postseason.[47] The team ended up with the 4th seed in the West after going winless in the round-robin portion of the Stanley Cup Qualifiers, they lost to the Vancouver Canucks during Round 1.On May 27, 2016, Parayko was chosen to be a part of Team North America, a selection of the top American and Canadian players aged 23 and under, at the 2016 World Cup of Hockey in Toronto.[5] After the Blues were eliminated in the second round of the 2017 Stanley Cup playoffs, Parayko joined Canada at the 2017 World Championship, where he registered seven points (three goals and four assists) and was named an All-Star.[55] Seven years later, with the Blues missing qualification to the 2024 Stanley Cup playoffs, Parayko rejoined Team Canada for the 2024 IIHF World Championship.
Parayko (far bottom right) scoring a power-play goal during a game against the
San Jose Sharks