At the time of Stearne’s birth, his grand-uncle, James Ussher, is Bishop of Meath. His father, John Stearne of Cambridge, who settled in County Down and married Mabel Bermingham, a niece of Ussher, is remote relation of Archbishop Richard Sterne.
Stearne enters Trinity College, Dublin at the age of fifteen in 1639, and obtains a scholarship in 1641. On the outbreak of the Irish Rebellion of 1641, Stearne leaves for England, and in 1643 goes to Cambridge, where he studies medicine at Sidney Sussex College, and collects material for his first work, Animi Medela. He remains at Cambridge about seven years, and then spends some time at Oxford, where he is welcomed by Seth Ward, then fellow of Wadham College. He is elected a fellow of Trinity College, Dublin in 1643, a position from which he is ejected by order of the Rump Parliament. Upon his return to Ireland in 1651 he is restored to his fellowship by Henry Cromwell, with whom he is on good terms, and to whom he dedicates one of his books.
In 1656 Stearne is appointed the first Hebrew lecturer in Trinity College, Dublin, receiving the degree of M.D. in 1658, and that of LL.D. in 1660. In 1659 he resigns his fellowship but is appointed to a senior fellowship in 1660, after the Restoration, receiving a dispensation from the statutes of the university respecting celibacy. He becomes in the same year professor of law. During his tenure of these various offices, Stearne practises as a physician in Dublin, obtaining special permission to reside outside the walls of the college.
Stearne is best known as the founder of the Irish College of Physicians. In 1660 he proposes to the university that Trinity Hall, situated in Back Lane, Dublin, then affiliated to the university, of which he has been constituted president in 1654, should be a college of physicians. The arrangement is sanctioned, and Stearne, on the nomination of the provost and senior fellows of Trinity College, in whom the appointment is vested, becomes its first president. No students are to be admitted who do not belong to Trinity College.
In 1662 Stearne is appointed for life professor of medicine in the university. In 1667 a charter is granted to the College of Physicians, under which a governing body of fourteen fellows is constituted, of whom Sir William Petty is one, with Stearne at their head as president for life.
Stearne dies in Dublin on November 18, 1669, and is buried, by his own request, in the chapel of Trinity College, where his epitaph, by his friend Henry Dodwell the elder, describes him as Philosophus, Medicus, summusque Theologus idem.