Born in Co. Cavan, Ireland in November 1738, he was the grandson of two Irish clergymen. He studied art in Dublin before moving with his family to Killibegs, Co. Kildare in 1758. In London from 1761 he made a name for himself as an artist and became an evangelical Christian following a visit to the Moorfield's Tabernacle. In 1765 he joined the Methodists in Dublin, became one of Wesley's correspondents and entertained him during his later visits to Dublin. He was prominent among those in the Dublin society who opposed the separation of Methodism from the Church of England. A broken leg, following a fall early in 1779, led to a serious loss of self-confidence and brought him a letter from Wesley encouraging him not to undervalue his god-given talents. He died in Dublin on 6 October 1806.
Brooke was the nephew of the author Henry Brooke (1703-1783) whose five-volume novel The Fool of Quality (1766-1770) was abridged by John Wesley (with the author's approval) and published in 1781 under the title The History of Henry, Earl of Moreland.