He was eldest son of George Dalrymple of Dalmahoy, fifth son of John Dalrymple, 1st Earl of Stair, and a baron of the court of exchequer of Scotland, by his wife Euphame, eldest daughter of Sir Andrew Myrton of Gogar.
John Dalrymple succeeded to the title as fifth earl on the death of his cousin William, William Dalrymple-Crichton, 5th Earl of Dumfries, 4th Earl of Stair, on 27 July 1768.