Although born in Scotland, Coyle represented the Republic of Ireland under-21 team. Regarding his choice to represent Ireland, Coyle stated "My ambition was to play at the highest level possible and, if I'm being totally honest, I didn't and still don't think I would have been good enough to play for Scotland. But the Irish watched me play six or seven times for Dumbarton and my first game for them was actually against Scotland." Coyle's debut was in February 1987; he opened the scoring within two minutes, with Scotland going on to win 4–1.
