Studied under J.J. McCarthy before establishing a partnership with John O’Neill as O’Neill & Byrne in 1869. After the death of O’Neill in 1883, he practised alone as W.H. Byrne until 1902. He then took his son Ralph Byrne into partnership. Responsible for many churches and banks in towns and villages across Ireland, his major Dublin work was the reconstruction of the South City Markets in George’s Street after a fire largely destroyed the interior.