Striker Youssef Mouihbi scored the only goal, converting a first half penalty to ensure the Tunisians avenged a similar loss in the reverse fixture a fortnight ago in Suez.
The third win at the group stage take Etoile’s tally to nine, two more than Ahly, who achieved the historic feat of becoming the first Egyptian side to lay their hands on the second-tier continental club championship, and are poised to defend the crown.
Ahly who handed starting roles to returnee right back, Ahmed Fathi and new recruit Saleh Gomaa, two of five additions to their squad, rarely troubled the Tunisians.
Algeria-born striker Baghdad Bounedjah, back to Etoile on a six month loan from Qatari side, Al Saad tormented the Ahly backline with his surging runs upfront.
Prior to the penalty, he forced Sherif Ekramy to make a save of his shot on the turn on 17 minutes and before his goal bound shot five minutes later deflected off Mohamed Naguib to corner.
On 26 minutes, Bounedjah was adjudged to have been fouled by Saad Samir in the vital area for a penalty which was easily converted by Mouihbi for the goal that guaranteed them the three points.
Veteran Emad Meteab had Ahly’s best chanced to draw level, but his low shot from a Fathi cross went wide.
Ahly introduced another new recruit, Ghanaian John Antwi and Amr Gamal in the second half but their presence could barely aid their quest for the equalizer, whilst Bounedjah was also guilty of wasting some chances at the other end.
8.8.2015 Etoile du Sahel (Tunisia) 1-0 Al Ahly (Egypt)
9.8.2015 16H30 Stade Malien (Mali) vs Esperance (Tunisia)
8.8.2015 Orlando Pirates (South Africa) 2-0 CS Sfaxien (Tunisia)
9.8.2015 15H30 AC Leopards (Congo) vs Zamalek (Egypt)