[1] Koistinen made his North American debut in the 2006–07 season, playing with the Predators affiliate, the Milwaukee Admirals.

Koistinen scored his first NHL goal against Fredrik Norrena of the Columbus Blue Jackets in a 4-3 victory on December 27, 2007.

During the regular season after 28 games scoring 7 goals and 17 points, KHL team Salavat Yulajev Ufa signed Koistinen to a 2-year deal.

[7] In June 2018 Koistinen was convicted of domestic abuse in Finland after he was found guilty of hitting, kicking, and strangling his wife, the couple had been married since 2007 and have two children.

It was also revealed that his sudden departure from SCL Tigers six months earlier was due to an extramarital affair with a young woman working for the club.