Diouf's international career started in April 2000 against Benin. He has earned 69 international caps and scored 21 goals for his country. He played for Senegal in their 2002 FIFA World Cup campaign and was elected to the World Cup All-Star team, after leading Senegal to the quarter-finals and victories over France (1–0) and Sweden (2–1). Senegal eventually lost 1–0 in extra time to Turkey. He was also part of the Senegal team who were the runners-up in the 2002 African Cup of Nations, but was one of the players who missed a penalty during the shootout in the final as they lost to Cameroon. Diouf was banned from international football for four matches in 2004 for a verbal assault on referee Ali Bujsaim.