Johan Tallgren was born in Helsinki in 1971. In 1991, he started study of composition at the Sibelius Academy with Paavo Heininen. He also attended classes led by composers such as Magnus Lindberg and Kaija Saariaho. In 1995, he participated in Voix Nouvelles at Royaumont, where he studied with Brian Ferneyhough and Michael Jarrell, returning there the following year.

His music has been performed at the Helsinki and Tampere Biennales and at Ars Musica in Brussels, by ensembles such as Ensemble Recherche, Zagros, and Kerberos. Tallgren served as president of the Korvat auki [Open Ears] Organisation, founded by Esa-Pekka Salonen, Kaija Saariaho, and Magnus Lindberg to support young composers in Helsinki. He moved to Paris in 1997.