Career
Pöysti began his career as a child actor, becoming known to the Finnish public as Olli Suominen in the "Suominen family" films. The first of these films as Suomisen Perhe (1941). Pöysti was 14 years old at the time of the film.
Pöysti matriculated in 1945 in the Helsinki Normal Lyceum.
During 1974–1981 he was the manager of the Tampere Workers" Theatre, and during 1981–1985 the manager of the Royal Dramatic Theatre in Stockholm. In his later career he has had many speaking roles in musical plays.
He has had many prominent roles on television, of which among the most notable are the leading roles in the Strindberg plays Gustav III (Finnish: Kustaa III) and Erik XIV. He has also read bedtime stories in children"s programs. In addition to his stage career, Pöysti has written several books, including his own memoirs.
Pöysti has lived in Paris, but currently he lives in Lauttasaari, Helsinki.
Lasse Pöysti"s son Tom Pöysti has also acted in many film and theatre roles.