Born at Maidstone in Kent on 15 May 1794, he was son of Abraham Harris, Unitarian minister at Swansea for 40 years.
In April 1817, Harris was invited to become minister of Renshaw Street Unitarian Chapel in Liverpool, then vacant by the resignation of Robert Lewin.
In the summer of 1821 a division occurred in the Bank Street Unitarian congregation, Bolton, and in 1822 Harris accepted an invitation to become minister of the seceders.
Harris was known in Manchester as ‘the intrepid champion of Socinianism.’ In 1822 he published The Lancashire and Cheshire Unitarian Association, and the Christian Reflector vindicated; in 1823 he published an account of the formation of the Moor Lane congregation, some statements in which provoked replies from other clergymen; and in 1824 appeared Christianity defended.
In September 1825 Harris resigned his charge in Bolton, and moved to Glasgow, his wife's native place.
He stayed four years, though with less success than in Glasgow, and in 1845 he accepted an invitation to become the minister of Hanover Square Chapel, Newcastle-upon-Tyne.
Harris was constantly writing, lecturing, or preaching, and advocating Sunday schools, benevolence funds, tract and book societies, and institutions for mutual improvement.