Born at Islandmagee, Co Antrim, he was educated at the Methodist College and Queen's College, Belfast, then still a constituent of the Royal University of Ireland, graduated in 1907 and served as demonstrator in anatomy. He served in France during the 1914-18 war as a surgical specialist with the rank of Captain RAMC. On return to civil life he was appointed in 1920 assistant surgeon and later surgeon to the Samaritan Hospital for Women, Belfast; on his retirement in 1949 he was appointed a governor of the hospital. He had a large consulting practice in obstetrics and gynaecology, and in 1926 was the first obstetric specialist appointed to the Belfast City Hospital, where he established a department which became the largest in the area. Holmes was largely responsible for the new Jubilee Maternity Hospital opened in 1935. He was a great clinical teacher, affectionately known as "Tommy". From 1939 to 1941 he was president of the Ulster Medical Society and in the war of 1939-45 kept open house at his home in Malone Road for doctors on war service. He was a member of the BMA for over fifty years, and he was vice-president of the Section of Obstetrics and Gynaecology at the 1937 Annual Meeting in Belfast. He maintained a keen interest in his old school and Rugby football, having captained the team which won the Ulster Schools' Cup in 1900; he was later captain of Collegians and played for Ulster. He was president of the Old Boys Association of his school in 1949. He also enjoyed shooting and fishing. He became great friends with his students and housemen, sharing their successes and failures, and when he was eighty was still receiving letters from past students from every part of the world. Thomas Holmes died in Belfast on 27 August 1964, survived by his wife, two daughters, and a son; his younger son had died on war service in the RAF.