Gilchrist represented Scotland at under-18, under-19, under-20 levels. He received his first full cap for Scotland against France in the 2013 Six Nations Championship at the Stade de France, aged 22. He was not selected to play in any of Scotland's 2014 Six Nations matches under Scott Johnson. Vern Cotter selected him for the 2014 Scotland rugby union tour of the Americas and South Africa. He captained Scotland for the first time on 20 June 2014 against Argentina, having scored his first international try against Canada the previous week.