He also played one season each for the Arizona Coyotes, Philadelphia Flyers, Columbus Blue Jackets, and Vancouver Canucks before returning to Edmonton in 2019; he was then traded to the Detroit Red Wings in 2020.

[7] As the NHL's youngest player in 2007–08,[8] he tallied 49 points in 79 games playing between wingers and fellow rookies Andrew Cogliano and Robert Nilsson on a combination dubbed the "Kid Line."

[10] The next season, 2008–09, Gagner recorded his first career NHL hat-trick and added an assist for a four-point game in an 8–1 win against the Colorado Avalanche on March 19, 2009.

On March 9, 2011, Gagner severed a tendon in his left hand while facing the Washington Capitals when teammate Ryan Jones caught him with a skate blade while jumping over the boards.

Several months later, on February 2, 2012, Gagner scored four goals and four assists against the Chicago Blackhawks, tying the team record of eight points in a game, previously set by Wayne Gretzky and Paul Coffey.

[15] On July 22, 2013, shortly after the end of the 2012–13 season, the Oilers signed Gagner to a three-year contract extension worth an average annual value of $4.8 million.

Gagner, however, only spent an hour as a member of the Lightning before then being acquired by the Arizona Coyotes, along with B. J. Crombeen, in exchange for a sixth-round pick in the 2015 NHL Entry Draft.

[17] During the Coyotes' training camp ahead of the 2014–15 season, Arizona head coach Dave Tippett experimented utilizing Gagner on the right wing instead of his natural centre position, where he played in a pre-season, 5–4 shootout victory over the Los Angeles Kings.

[18] With a fresh start, former with Arizona, Gagner found chemistry playing on a line with centre Martin Hanzal; the two combined for 16 points in just five games in December and January 2015.

[19] On June 27, 2015, Gagner was traded to the Philadelphia Flyers along with a conditional third (2017) or fourth (2016) round draft pick in return for Nicklas Grossmann and the contract of Chris Pronger.

[20] Coyotes general manager Don Maloney explained the trade as being due to a belief in the organization that Gagner "couldn't play centre at the NHL level".

[32] As a free agent from the Red Wings, Gagner continued his career by signing for his 16th season in the NHL in agreeing to a one-year, league minimum $750,000 contract with the Winnipeg Jets on September 2, 2022.

[43] Gagner played in both of Canada's group stage games, registering an assist in the opener against the tournament hosts, HC Davos,[44] before featuring in their semi-final loss to Straubing Tigers.

[45] In his rookie year, Gagner lived in a house provided by Oilers captain Ethan Moreau, along with teammates Andrew Cogliano and Tom Gilbert.

Due to his dad's career, Sam Gagner grew up in Minneapolis, Dallas, Toronto, Calgary, Miami, Vancouver and Oakville.