Sinclair was included in the Jamaica squad at the 1998 FIFA World Cup held in France, making history as they became the first English-speaking Caribbean country to qualify for a World Cup. He started in all three group matches against Croatia, Argentina and Japan. Jamaica lost the opening two games but claimed their first ever points at a World Cup with the 2–1 victory over Japan in Lyon, but were still eliminated finishing third in the group. Over the next couple of years Sinclair represented the side in a number of friendly matches and was included in the squad for the 2000 CONCACAF Gold Cup. He played in the two group stage matches, a 1–0 defeat to Colombia and 2–0 defeat to Honduras as Jamaica were knocked out at the first stage.