 Mackin was involved in two matches with the Wales under-17 team, against Scotland and Norway in 2001 and 2002 respectively, although he did not play in either and remained on the substitutes' bench.He was called up for a training camp and match against Bosnia and Herzegovina in the 2003 UEFA European Under-17 Championship first qualifying round, and made an appearance in this match as Wales won 2–1 to progress to the second qualifying round.He was called into the under-19 team for the Milk Cup in July 2004 and another call up came for the 2005 UEFA European Under-19 Championship qualifier against the Faroe Islands in October.