Wallstedt played junior ice hockey with his hometown club, Västerås IK, before joining Luleå HF organization for the 2018–19 season.

He entered in the second period of the game in relief of David Rautio, and allowed one goal as Luleå fell to HV71 by a score of 2–1.

[1] On May 17, 2022, Wallstedt was signed by the Minnesota Wild to a three-year, entry-level contract.

[3] During the 2023–24 season, on 10 January 2024, Wallstedt made his NHL debut in a 7–2 loss to the Dallas Stars, also becoming the youngest goaltender in the Wild's history.

This biographical article relating to a Swedish ice hockey goaltender is a stub.