A native of Walpole, Massachusetts, Chris Wagner set the single-season scoring record for the Eastern Junior Hockey League by recording 83 points (34 goals, 49 assists) in 44 games for South Shore. That was enough to attract the attention of the Anaheim Ducks, who selected him in the fifth round (No. 122) of the 2010 NHL Draft.

The following season, Wagner opted to attend Colgate University, where he had 19 points (nine goals, 10 assists) as a freshman before breaking out with 51 points (17 goals, 34 assists) in 38 games as a sophomore in 2011-12, the most points by any underclassman in NCAA Division I hockey that season.

On April 3, 2012, he a three-year, entry-level contract with the Ducks and played the majority of the following three season with Norfolk of the American Hockey League.

After playing nine NHL games in 2014-15, Wagner made the Ducks out of training camp in the fall of 2015, but played in 11 games before being claimed off waivers by the Colorado Avalanche on Nov. 15, 2015. He scored his first NHL goal 10 days later for the Avalanche in a 5-3 loss to the Ottawa Senators.

After scoring four goals in 26 games with Colorado, Wagner was again placed on waivers and claimed back by the Ducks on Feb. 25, 2016.

Although he again split time with Anaheim and San Diego of the AHL in 2016-17, Wagner scored three goals in 17 Stanley Cup Playoff games to help Anaheim advance to the Western Conference Final.

The following season, Wagner was traded to the New York Islanders for Jason Chimera on Feb. 26, 2018, and after finishing the season on Long Island, he signed with the Boston Bruins as a free agent on July 1, 2018.

In his first season with the Bruins, Wagner had 19 points (12 goals, seven assists) in 76 regular-season games, and he scored twice in 12 playoff games to help them advance to the Cup Final, where they lost to the St. Louis Blues in seven games.