Mouloungui began his career in his native Gabon at Mangasport Moanda, before moving to CFA 2 side Vauban Strasbourg, France in 2002. Here he spent a year before signing for RC Strasbourg, then of the French top flight.
For first half of the 2005/06 season Mouloungui gained first-team experience on loan to FC Gueugnon in Ligue 2 before returning to his Alsace based parent club in January 2006. Here he made two first team appearances, not scoring, as Strasbourg were relegated to Ligue 2.
In the 2006/07 season he was top goal scorer for his side with 11 goals from 30 games, helping the club make a swift return to the French top flight, after just one season spent in the second tier. He became first choice forward for his club, starting Strasbourg's first Ligue 1 game in the 2007/08 season alongside on-loan FC Porto striker Wason Rentería against French giants Marseille with the game ending in a 0–0 draw.