Fullarton obtained the degree of Master of Arts from Glasgow University in 1665. Following his ordination, he was minister at Kilmodan from 1669 to 1684 and at Paisley between 1684 and 1689, whence he was ejected at the Revolution. Robert Wodrow recorded in 1703 that Fullarton was present with other Episcopal clergy at a service in Glasgow to commemorate the execution of Charles I, and he also preached there. The connection with Paisley had not been broken, and Fullarton was at the deathbed of the young Lady Dundonald in Paisley in 1710, and later celebrated Holy Communion for the widowed Earl in Paisley Abbey, "the first instance of Communion at Yule so openly celebrated in this country," according to Wodrow. By 1712, Wodrow considered Fullarton to be "the man of that [Episcopalian] party in most repute in this country."