On 17 November 2004, Hammell made his full international debut for Scotland under caretaker manager Tommy Burns in a 4–1 friendly defeat to Sweden, coming on as a 54th-minute substitute for Hearts centre-back Andy Webster. In May 2013, after a nine-year absence from international duty, Hammell was drafted in to the Scotland squad for their FIFA World Cup qualifier against Croatia following injury doubts over other full backs. In July 2013, Hammell managed to retain his place in the Scotland squad to face England at Wembley in August. Hammell received another late call up to the Scotland squad for the return fixture against Croatia in October 2013.