During World War I, MacGill serves with the London Irish Rifles (1/18th Battalion, London Regiment) and is wounded at the Battle of Loos on October 28, 1915. He is recruited into Military Intelligence, and writes for MI 7b between 1916 and the Armistice in 1918. He writes a memoir-type novel called Children of the Dead End.
In early 2008, a docu-drama starring Stephen Rea is made about the life of Patrick MacGill, which is released in Ireland in 2009 as Child of the Dead End. One of the film’s locations is the boathouse of Edinburgh Canal Society at Edinburgh on the Union Canal, and one of its rowing boats.
An annual literary MacGill Summer School is held in Glenties in mid-July each year in his honour. A statue in his honour is on the bridge where the main street crosses the river in Glenties. He has three children, Christine, Patricia and Sheila MacGill.