Free church
Moncreiff took part in the controversy which ended in the disruption of 1843. He joined the Free Church in June 1843, and from that date till 1852 he was the minister of Free East Kilbride. He succeeded to the baronetcy and assumed the name Wellwood on the death of his father in 1851. In 1852 he became minister of Free St. Cuthbert's in Edinburgh (his grandfather, Rev Sir Henry Moncreiff (1750-1827) had passed 50 years of his ministry at St Cuthbert's Church, Edinburgh). He was appointed joint principal clerk to the Free General Assembly in 1855, was created DD by the University of Glasgow in 1860, and appointed moderator of the Free church Assembly in 1869. In 1862 he was appointed secretary of the Bible Board, and held that office at his death, which took place 4 November 1883.