Östman has been a Member of Parliament representing the Constituency of Vaasa since 2011. He is a member of the Grand Committee, the Working Subcommittee of the Grand Committee, the Legal Affairs Committee and the Finnish Delegation to the Nordic Council. Previously, he was a member of the Finance Committee and the Agriculture and Forestry Committee. He has also been Secretary General and Vice Chairman of the Christian Democrats.[4] In 2004, he was a candidate for the Chair of the Christian Democrats, losing to Päivi Räsänen.[5]
Östman supports the maintenance of Larsmo's bilingual status. His candidacy to become the vice chair of the party was supported by the Christian Democrats' Swedish-speaking organization.[6]