Johann I was the brother of Jakob I Bernoulli and was born in Basel, Switzerland. As in the case of several of the Bernoulli family Johann I's father did not encourage him to make a career of mathematics and he graduated in medicine in 1694.

Once he had abandoned medicine for mathematics he became chiefly interested in applying the calculus to physical problems. He played an important role as a propagandist for the calculus in general and in particular as a champion of Gottfried Leibniz's priority over Isaac Newton. Johann I held a chair in mathematics at Groningen, Holland, from 1695 and returned to Switzerland to take up a chair in mathematics at Basel on the death of his brother in 1705. Johann I's interests ranged over many fields outside mathematics including physics, chemistry, and astronomy. His mathematical work also included particularly important contributions to optics, to the theory of differential equations, and to the mathematics of ship sails.