In 2015, Mattocks was included in Jamaica's squads for the Copa América and CONCACAF Gold Cup tournaments. On 22 July 2015, Mattocks scored the opening goal in the 2–1 semi-final victory over the United States in Atlanta, Georgia, as the "Reggae Boyz" qualified for their first ever Gold Cup final. He also scored in the 3–1 defeat to Mexico in the final in Philadelphia.