African champions Hearts of Oak needed to come back from a goal down, thanks to a hat-trick by star striker Emmanuel Kuffour, as they opened the defence of their title.
The Ghanaian side left the comeback very late, though, after Kuffour had equalised two minutes before half-time.
Hearts missed several chances and were stopped from scoring more goals by an excellent Congolese keeper, Ghislain Kinkoukoudi.
Etoile took the lead after 14 minutes after Stephen Tetteh scored an own goal as he stretched to clear a shot by Mesmin Mbama.
Hearts were unable to get their game together after conceding the goal, but the best part of the second half featured a catalogue of wasted opportunities.
Charles Taylor tried a stylish flick with the side of his foot in front of goal and he hit the bar with two minutes left to play.
Kinkoukoudi denied Ishmael Addo and Kuffour early from the restart. Addo missed from a quickly played free-kick, while Kuffour chested down with only the Kinkoukoudi to beat, but the keeper blocked.
But in the space of two minutes Kuffour gave his side the much-needed breathing space to travel to Brazzaville for the second leg.
In the 82nd minute, Kuffour was on target for his second goal with a low diving header.
The striker, who has returned from Ukraine after failing a medical during trials and may need an operation to remove a gallstone, could not celebrate the goal because Etoile defender Armel Atshono was seen by the assistant referee to stamp on the player.
The Nigerian referee sent off Armel and within seconds Kuffour completed his hat-trick from a rebound after Kinkoukoudi failed to handle properly.
Hearts will play the second leg on Sunday in Congo. The match was postponed twice by CAF upon the request of the African champions.