Kilcoyne was named in Ireland's training squad for the 2013 Six Nations Championship on 17 January 2013. He started for Ireland Wolfhounds in their friendly against England Saxons on 25 January 2013. Kilcoyne made his Six Nations debut on 2 February 2013, coming on as a replacement in Ireland opening 30–22 win against Wales. He again came on as a replacement against England on 10 February 2013, Scotland on 24 February 2013, and Italy on 16 March 2013.