In 1725, on Stephen James's death and before his own ordination, he acted as assistant in the ministry to Robert Darch, at Hull Bishops, and in the Taunton Academy to Grove.
A list of his students is given in the Monthly Repository, 1818; there were more men of mark under Grove; Amory's best pupils were Thomas and John Wright of Bristol.
He moved to London in October 1759 to become afternoon preacher at the Old Jewry meeting-house, and in 1766 succeeded Samuel Chandler as co-pastor of the congregation with Nathaniel White.
in 1768, and was Tuesday lecturer at Salters' Hall from 1768, and morning preacher at Newington Green, as colleague with Dr. Richard Price, from 1770, in addition to his other duties.
Amory, like many others, had in point of fact never subscribed, and he had to combat the opposition of his friends, who thought, with Joseph Priestley, that a subscription not rigidly enforced was better than a new declaration (that they received the Scriptures as containing a divine revelation), which might be pressed in the interests of intolerance.
The inscription on his tomb speaks of him as 'having been employed for more than fifty years in humbly endeavouring to discover the religion of Jesus Christ in its origin and purity.'