He was a long-term member of the Finnish Parliament and the minister of interior between 1970 and 1971.
[3] During his term at the Parliament he represented first Vaasa County and then Central Finland.
[1] He was appointed interior minister on 15 July 1970 and remained in the post until 27 May 1971.
[3] He was part of the second cabinet of Prime Minister Ahti Karjalainen.
[1] Then Jämsén was named the governor of Central Finland and served in the post between 1971 and 1976.