Andersson, 19, was selected by the Rangers in the first round (No. 7) of the 2017 NHL Draft after he had 19 points (nine goals, 10 assists) in 42 games with HV71, helping the team win the Le Mat Trophy as Swedish Hockey League champions.

On July 13, 2017, Andersson signed a three-year, entry-level contract with the Rangers. He had 14 points (five goals, nine assists) in 25 games with Harford of the American Hockey League before he was called up to New York on March 25, 2018.

In his first game against the Washington Capitals the following day, Andersson became the youngest player in the history of the Rangers to score a goal in his first NHL game. Andersson (19 years, 164 days) passed the mark previously set by Mike Allison (19 years, 195 days), who did it on Oct. 9, 1980 against the Boston Bruins.

On April 29, 2018, Andersson was named to Sweden's roster for the 2018 IIHF World Championship. He had two points (one goal, one assist) in 10 games to help Sweden win the gold medal.