Díaz was included in Colombia's squad for the 2021 Copa América. On 23 June, he scored the opening goal in a 2–1 first round loss to hosts Brazil with an acrobatic volley. On 6 July, Díaz scored Colombia's only goal in their semi-final match against Argentina, which ended in an Argentine victory following a penalty shoot-out. Three days later, he scored twice, including the match-winning goal, in a 3–2 victory over Peru in the third-place match of the tournament. He would end as joint top goal scorer of the tournament alongside Lionel Messi.