McCloskey received his first call up to the senior Ireland squad by coach Joe Schmidt for the 2016 Six Nations Championship. On 27 February 2016 he was included in the Ireland starting 15 for the first time in the 21-10 defeat against England at Twickenham. McCloskey had to wait until 18 November 2017 for his next call up to the Irish team. He was selected for the second test against Fiji in the inside centre berth, and he played the full 80 minutes in a 23-20 win.