Aside from a minor role in the Battle of Jutland in May 1916 and the inconclusive Action of 19 August the same year, "Erin"s service during the war generally consisted of routine patrols and training in the North Sea. The ship was deemed obsolete after the war; she was reduced to reserve and used as a training ship. "Erin" served as the flagship of the reserve fleet at the Nore for most of 1920. She was sold for scrap in 1922 and broken up the following year.