About 1809, he applied to the London Missionary Society. After conferring with a group of ministers at Aberdeen, he was sent to Gosport, where he studied under David Bogue for three years. Ordained as a missionary to China on 16 July 1812 at Rev. John Griffin's church at Portsea, Portsmouth, Milne proposed "to go from house to house, from village to village, from town to town, and from country to country, where access may be gained, in order to preach the Gospel to all who will not turn away their ear from it."