Although Mulholland later claimed that at the Battle of Gettysburg on July 2, 1863 he personally took command of the 140th Pennsylvania Infantry and led it into action, this fact is mentioned in neither his own official report of the battle, nor that of the lieutenant colonel commanding the 140th. When the 116th was returned to full strength in early 1864, he was promoted to colonel. He was wounded a second time at the Battle of the Wilderness, May 5, 1864. At Po River he was wounded a third time, but remained in hospital only ten days. Resuming his command, he was dangerously wounded again at the Battle of Totopotomoy Creek. He recovered rapidly and commanded his brigade in all the actions around Petersburg, particularly distinguishing himself by storming a fort on the Boydton Plank Road. Mulholland was mustered out of the volunteer service on June 3, 1865.