He has appeared in more than ten films starting with his first appearance in a small role in The Best Intentions (1992) directed by Bille August. He is best known for his appearance in Together (2000) directed by Lukas Moodysson.
Hammarsten made his international film début in Brüno (2009) as Lutz, the title character's sidekick.
In Swedish television he became known through the comedy show Cleo. He has also made numerous appearances in television programs. He appeared in the first episode of Crimes of Passion. Since 2013 he acts in the series Fröken Frimans krig. He will participate in Let's Dance 2018 broadcast on TV4.
