Adam was called up by national manager Alex McLeish to the Scotland squad for the first time on 11 May 2007 for a friendly against Austria and a Euro 2008 qualifying Group B match against the Faroe Islands. He made his debut at the Gerhard Hanappi Stadium in Vienna on 30 May as a 67th-minute substitute, in a 1–0 victory. He then made his competitive debut as a 77th-minute substitute in a 2–0 win over the Faroe Islands at the Svangaskarð stadium in Toftir on 6 June.