William was born at Rushay in the parish of Bagber, Dorset, he was son of a farmer. After being a solicitor's clerk and for a while keeping a school at Mere in Wiltshire, he was put into the Church of England in 1847, taking a BD degree from St John's College, Cambridge, in 1851.He then served curacies at Whitcombe Church in Whitcombe, Dorset, 1847–52, and again from 1862. Between 1860–62 he held a curacy at Rotherham in Yorkshire. He became rector of St Peter's Church, Winterborne Came with Winterbourne Farringdon, Dorset, from 1862–86. He is buried in the churchyard beneath a Celtic cross. The plinth of the cross has the inscription: 'In Memory of William Barnes, Died 7 October 1886. Aged 86 Years. For 24 Years Rector of this Parish. This Memorial was raised to his Memory by his Children and Grandchildren.