He studied at Uppsala University, graduated as filosofie magister (M.A.)

He became church pastor in the parish of Näs in Västergötland followed by several years visiting foreign universities.

He was appointed Doctor of Theology in 1725, Bishop of Gothenburg 1731–1744 and succeeded his elder brother Erik Benzelius the Younger (1675–1743) as Archbishop of Uppsala in 1744.

He was succeeded as Archbishop by his younger brother Henric Benzelius (1689–1758).

[2][3] Jacob Benzelius wrote several influential books on theology.