In a hotly contested clash at the Stade Denis Sassou Nguesso, Leopards managed to nullify a Cotonsport attack that had netted five goals in their opening two games.
The Cameroon Elite One champions are yet to lose in this year's competition after dropping down from the Champions League in April, but this was the first time they have failed to win in the group stages.
Having seen their original meeting in May postponed due to an Africa Cup of Nations clash between Congo and Namibia, top spot in the group was up for grabs in Dolisie with only two points separating them.
However, neither side could break the deadlock in the rearranged fixture meaning they strengthen their grip on the top two places.
With Cotonsport clear at the top, Leopards, the 2012 winners, are now three points clear of ASEC Mimosas in third place at the halfway point in the group.
