Colonialist. Born at Tullibody (Clackmannanshire), the third son of an Advocate, Abercromby was educated in London and Leiden, and studied law before leaving for North America c.1730. He settled in South Carolina and was soon appointed Attorney-General of that colony. He served as a member of the South Carolina Assembly (1739-45).
Returning to Britain, he lived mostly in London but maintained estates in Scotland, at Brucefield (Clackmannanshire) and Bandeath on the opposite bank of the River Forth from his family estates at Tullibody. He served as the Colonial Agent for North Carolina and Virginia (1748-73) and was Deputy Auditor-General of Plantations (1751-73), resisting French expansionism in North America and the West Indies. He also served as Member of Parliament for Clackmannanshire (1761-68).
He died despondent at the revolutionary fervour which had brought war to the American Colonies, to which he had dedicated his life. He was the great-uncle of noted general Sir Ralph Abercromby (1734 - 1801).