Diao has appeared 39 times for Senegal, scoring four goals in the process since 2000, including a strike against Denmark at the 2002 FIFA World Cup after a series of quick passes by his team mates to set him up. He was later sent off in the same match was a high tackle. Diao was in the Senegal squad that went to the 2002 African Cup of Nations were Senegal finished second after losing in the final to Cameroon and was part of the Senegal side that went to the 2004 African Cup of Nations.