Johan Larsson was selected by the Minnesota Wild in the second round (No. 56) of the 2010 NHL Draft after getting 34 points (15 goals, 19 assists) in 40 games with Brynas in Sweden's junior hockey league.

After playing two more seasons in his native Sweden, Larsson came over to North America in 2012-13. The 5-foot-11, 204-pound forward played that season with Houston of the American Hockey League, where he had 37 points (15 goals, 22 assists) in 62 games. Larsson also made his NHL debut with the Wild on Feb. 17, 2013, playing 14:02 in a 3-2 win against the Detroit Red Wings.

However, after the season Larsson was traded to the Buffalo Sabres as part of the package for Jason Pominville on April 3, 2013.

Larsson split the 2013-14 and 2014-15 seasons between the Sabres and Rochester of the AHL, but he cracked the Sabres lineup for good in 2015-16, when he had 17 points (10 goals, seven assists) in 74 games.

The following season for Larsson ended prematurely after he dislocated his wrist and elbow on New Year's Eve and required season-ending surgery. He would bounce back though, playing in 80 and 73 games, respectively in each of the next two seasons.

In 2019-20, Larsson had an NHL career-high 18 points (six goals, 12 assists) in 62 games before the season was paused on March 12 due to concerns surrounding the coronavirus.