Connolly started Ireland's opening group match vs China U23 and marked it with a goal and an assist for Zak Elbouzedi in a 4–1 win. On 5 October 2019, the same day he scored twice against Tottenham, he received his first call-up for the Republic of Ireland senior team for the Euro 2020 qualifying matches against Georgia and Switzerland. He made his debut against Georgia on 12 October 2019, replacing James Collins when he came on as a substitute in the 79th minute in the 0–0 away draw.