In June 2011, Mulgrew stated that he would consider playing for the United States, whom he was qualified to play for due to an American-born grandmother, if he was continually overlooked for Scotland. In February 2012, Scotland manager Craig Levein handed Mulgrew his first call-up to the senior squad, and he made his international debut on 29 February, starting at left back in a 1–1 draw with Slovenia. He also played in a 5–1 defeat to the USA in Florida in May 2012.