Costa received his first call-up to the senior Portugal squad ahead of the UEFA Nations League fixtures in October 2018. He made his senior international debut in a friendly against Scotland at Hampden Park on 14 October 2018 in a 3–1 win in which he scored the opening goal. Portugal would go on to win the 2018–19 UEFA Nations League after defeating the Netherlands 1–0 in the final match. However, Costa was not named to the squad for the final nor semi-final.