McCallan made his debut for Ireland on 2 June 1996, playing against Wales in Dublin, taking a wicket with his first delivery. He scored his first century in his following match, against the MCC in Malahide. He made his List A debut later in the month, playing in the NatWest Trophy against Sussex. He was named in the Ireland squad for the 1996 Triple Crown Tournament in Wales, but only played one match, against the hosts. He was also named in Ireland's squad for the first European Championship that year, again playing just one game, against Gibraltar. The year finished for McCallan with a match against Scotland, which marked his first-class debut.