He has played for Le Havre and FC Sochaux-Montbéliard. Diawara was dropped from the Senegal squad in August 2006, ahead of their friendly with Côte d'Ivoire, due to a breach of discipline.
Diawara signed for Charlton Athletic on a four-year deal for £3.712m on 30 August 2006.However things did not work out with the Charlton Athletic Chairman criticising manager Iain Dowie's signing of the player, "We backed Iain, they were his signings, but I had never heard of Souleymane Diawara, apparently the best centre-half you've never heard of".
Since then Souleymane has returned to France and won the French league title twice in three years; with Bordeaux and then Marseille.