Hischier became the highest-drafted Switzerland-born player in NHL history when the Devils selected him No. 1 in the 2017 NHL Draft. He took his NHL career to another level in 2024-25 by scoring 35 goals and getting named to Team Switzerland's preliminary roster for the Olympic Winter Games Milano Cortina 2026.

In his first season in North America with Halifax of the Quebec Major Junior Hockey League (2016-17), he was named Canadian Hockey League rookie of the year and won both the Michael Bossy Trophy as the best professional prospect and Michel Bergeron Trophy as offensive rookie of the year after scoring 86 points (38 goals, 48 assists) in 57 games.

Hischier scored his first two NHL goals against the Ottawa Senators on Oct. 19, 2017, and finished with 52 points (20 goals, 32 assists) in 82 games as a rookie in 2017-18. He scored 47 points (17 goals, 30 assists) in 69 games the following season.

Hischier was named to the NHL All-Star Game for the first time in 2020; he had 36 points (14 goals, 22 assists) in 58 games for New Jersey before the season was paused March 12 due to concerns surrounding the coronavirus.

Hischier was named the 12th captain in Devils history on Feb. 20, 2021. At 22 years and 47 days old, he became the second-youngest Devil to hold the position (Kirk Muller, 21 years and 243 days) and joined Nashville Predators defenseman Roman Josi as the second Switzerland-born captain in the NHL.

Hischier ranked second among Devils forwards in ice time per game (19:17), first in short-handed ice time per game (2:06) and takeaways (64), and second in blocked shots (61), won 53.9 percent of face-offs (third) and 57.8 percent of defensive draws (second), and had NHL career highs of 31 goals, 49 assists and 80 points in 2022-23. He was nominated for the Selke Award, given annually to the forward voted best to excel in the defensive aspects of the game as voted on by the Professional Hockey Writers' Association, for the first time.

On the international stage, Hischier scored seven points (four goals, three assists) in five games for Switzerland at the 2017 IIHF World Junior Championship, including two goals against the United States in the quarterfinal round.