First-half goals from Carl Medjani and Johan Cavalli earned Ajaccio their second win of the Ligue 1 season.
Cavalli delivered the corner from which defender Medjani headed the opener, and then added a close-range second before the interval.
Evian pressed in the second half, looking for a way back into the game, but remain on only one point after four games.
Ajaccio had an early chance to open the scoring when the influential Cavalli played in Eduardo, who volleyed just wide.
The goal came in the 20th minute when Cavalli's corner to the far post was met by Medjani, whose header beat keeper Bertrand Laquait and Olivier Sorlin on the line.
Cavalli had the chance to add his own name to the scoresheet in spectacular fashion when he met Samuel Bouhours' cross with a left-foot volley which flashed just wide of the post.
His goal, when it came in the 41st minute, was a more low-key affair as Laquait saved Sigamary Diarra's shot and Cavalli followed up to slot home.
Evian needed to find a response early in the second half, and their first chance came through Cedric Barbosa's free-kick which was blocked by the home defence.
Sorlin was next to chance his arm from a similar situation, but keeper Guillermo Ochoa saved.
The Mexican was soon into the action again, saving from Saber Khelifa after he was teed up by Barbosa on the edge of the box.
But Evian's threat dissipated after the hour mark and it was Ajaccio who had a late chance to add a third, but a flowing move ended with Laquait saving Diarra's 20-yard effort.