In February 2015, Republic of Ireland manager Martin O'Neill said that Arter was on his radar and could be called up to the squad for the UEFA Euro 2016 qualifying match against Poland. He earned his first call-up for that match on 12 March, following what O'Neill described as a "very good season", but did not play in it. He made his senior debut on 7 June 2015, as a 63rd-minute substitute for Glenn Whelan in a 0–0 draw in a friendly against England at the Aviva Stadium. He made his full international debut against the Netherlands in a 1–1 draw in Dublin on 27 May 2016, in which he was awarded man of the match. However, he was ultimately left out of Ireland's squad for UEFA Euro 2016. Arter made his senior competitive debut for the Republic of Ireland in a 1–0 away win over Austria on 12 November 2016 in a World Cup qualifying match, having made himself unavailable for the previous month's matches against Georgia and Moldova.