Ostlund was the 16th overall pick of the Sabres in the 2022 NHL Entry Draft and has yet to play an NHL game. He spent the 2023-24 season with Vaxjo HC (SweHL), scoring 23 points (12G / 11A) in 38 games.

The Sabres selected Ostlund with the No.16 overall pick in this summer's NHL Draft. The Swedish centre had nine goals and 33 assists (42 points) in 32 games with Djurgardens Jr. (J20 SuperElit) in 2022.