In 1762 Palmer became afternoon preacher to the independent (originally presbyterian) congregation at Mare Street, Hackney, and was ordained on 21 November 1763.
He then succeeded William Hunt as morning preacher at Mare Street, and remained in charge of the congregation, which moved in 1771 to St. Thomas's Square, until his death.
Henry Forster Burder was his assistant from October 1811; but Palmer remained active in his charge to the last, preaching on the Sunday before his death.
It was too long for its original purpose, and Palmer issued The Protestant Dissenters' Shorter Catechism … a Supplement to the Assembly's, 1783.
At Orton's suggestion Palmer undertook an abridgment of the Account of the Ministers … Ejected (1713), by Edmund Calamy, incorporating the Continuation of 1727.
(1778), John Howard (1790), Habakkuk Crabb (1795), and other sermons (1774–90); also: He edited, with notes, Samuel Johnson's Life of Isaac Watts, 1785, and Orton's Letters to Dissenting Ministers, 1806, 2 vols., with memoir.
His life of Samuel Clark, the Daventry tutor, is in the Monthly Repository, 1806; that of Caleb Ashworth, is in the same magazine, 1813.