At Euro 2016, Allen set-up Aaron Ramsey's goal in a 3–0 win over Russia on 20 June, which allowed Wales to top their group and advance to the knockout round of the tournament. Wales were eliminated following a 2–0 defeat to eventual champions Portugal in the semi-final on 6 July. Allen was named to the team of the tournament for his performances. In May 2021 he was selected for the Wales squad for the delayed UEFA Euro 2020 tournament.