James Buchanan was born in Paisley on 14 April 1804 as the son of a wine merchant. After studies in Glasgow and Edinburgh, he was ordained minister of the Church of Scotland at Roslin in 1827 and received the parish of North Leith in 1828, where he attained great fame as a preacher. In 1829 he married Elizabeth, daughter of John Cochrane, a Glasgow merchant; they had a son and a daughter before her early death in May 1832. In 1836, he married Mary, daughter of John Morison, with whom he had a daughter. In 1840, Buchanan was called to St Giles's Church, Edinburgh, but joined the Free Church of Scotland following the Disruption of 1843, ministering at St Stephen's Free Church until 1845. In 1845, he was appointed professor of apologetics at the New College of the Free Church in Edinburgh, and succeeded Thomas Chalmers as professor of systematic theology in 1847, which he held until 1868. He died on 19 April 1870 at 51 Lauriston Place, Edinburgh.