[2] In the 2020–21 season with HPK, Puustinen recorded 21 goals and 20 assists for 41 points in 51 games.

On 6 May 2021, Puustinen was signed by the Pittsburgh Penguins to a two-year, entry-level contract.

He scored his first NHL point that night, a secondary assist on Jeff Carter's goal, as the Penguins won 5–2.

[5] During the 2023–24 season, on 27 December 2023, Puustinen scored his first NHL goal in a 7–0 victory over the New York Islanders.

This biographical article relating to a Finnish ice hockey winger is a stub.