Ghana defender Harrison Afful scored the match winner as Esperance beat Cosmos de Bafia 1-0 in Douala on Sunday in the first leg of their CAF Champions League?s round of 32 tie.
Afful netted on the stroke of full time secured the victory for the visitors at the Reunification Stadium.
He was at the last post to connect with a simple tap-in a cross from the left.
There was scare for Esperance in the 56th minute but Comos de Bafia?s opener was disallowed as the ball had gone out of play.
Ahmed Akaichi fired home in added time but the flag had gone up for an offside position.
The Tunisian giants will try to finish the job when they host Cosmos in Rad?s in the return leg in three weeks time.