For the 1988 African Cup of Nations, Okosieme remained part of the team and scored in a 3–0 first round win over Kenya. He started the 1–0 defeat to rivals Cameroon in the Final at Stade Mohamed V, Casablanca. It was reported that Okosieme produced a "mesmerising" performance and that Henry Nwosu's headed 'goal' from Okosieme's right–wing cross was controversially ruled out by the referee.