[1] Gezelius was born at Tillberga in the parish of Romfartuna (now Västerås) in Västmanland, Sweden.

Gezelius was a peasant's son, but was observed in childhood to have apparent gifts and was given a personal tutor, Boetius Murenius.

Subsequently, he worked as a grammar school in Västerås as a lecturer in theology and vicar at Stora Skedvi in Säter, Sweden.

[2] Gezelius published a number of textbooks and devoted his thesis in theology.

Johannes Gezelius the elder was known as an opponent of Finnish paganism and in 1673 ordered the destruction of spells.