The hosts started the game brightly as Yassine Chikhaoui forced Charles Itandje into a smart stop with a fierce drive from inside the area in the opening minute, while Cameroon's Pierre Webo missed a gilt-edged chance in the second half, but neither side was able to break the deadlock.
After speculation surrounding Samuel Eto'o's international future, the forward was named in Cameroon's starting XI by Volker Finke.
However, the Chelsea man rarely threatened, and there is still all to play for in the second leg on November 17.
Houcine Ragued and Saber Khalifa both saw headers saved by Itandje shortly after Chikhaoui's early opportunity as Tunisia continued to apply the pressure.
After Eto'o saw a tame effort easily saved by Moez Ben Cherifia, Wissem Ben Yahia's dipping effort had Itandje scrambling once more to keep the scores level.
Jean Makoun almost put the visitors ahead four minutes from the break but put his effort past Ben Cherifia's left-hand post.
Cameroon, seeking to book a place in their seventh World Cup finals, also struggled to assert themselves after the break, with Ben Youssef heading a Sameh Derbaly cross just wide after 55 minutes.
But Webo then missed the best chance of the game as he failed to convert an Allan Nyom delivery into an open goal with 22 minutes remaining.
However, although the game became more open in the latter stages, the tie remains finely poised ahead of the second leg in Yaounde.
