He was the nephew of Anders Chydenius and the father of Johan Magnus af Tengström [fi], a zoologist, and uncle of Johan Jakob Tengström [fi], a historian and Fredrika Runeberg, a novelist.

In 1796, he became a member of the society Pro Fide et Christianismo, founded to promote Christian education.

He also became chairman of a committee that drafted proposals for supreme governance for the Grand Duchy of Finland.

Tengström's good relationship with Emperor Alexander I influenced the development of the Grand Duchy of Finland.

The ecclesiastical books were under revision in Sweden when the war broke out and the reforms in Finland were led by Tengström.