Tunisia, who lost the two-legged tie 4-1 on aggregate, argued Joel Matip, who played in the first leg, and Eric Choupo Moting, who came on as a substitute in both matches, should not have been playing.
"FIFA communicated to Tunisia Football Federation today that no breach of the FIFA regulations has been committed by the Cameroon Football Federation in relation to the matter at hand," said FIFA in a statement.
Tunisia's protest was reportedly over whether the two players, both born in Germany, were qualified to play for Cameroon at senior level.
Tunisia only reached the playoff because their 2-0 defeat at home to Cape Verde was overturned after the visitors were found guilty of fielding an ineligible player.
Cape Verde, who lost top spot in Group B to Tunisia after the North Africans were awarded a 3-0 win by forfeit, lost their appeal at FIFA and have taken the case to the Court of Arbitration for Sport
A total of nine matches were forfeited in the African qualifying competition because of ineligible players.
Cameroon, who have now qualified for next year's World Cup finals, were also among those to benefit when their 2-0 defeat to Togo in Group I was overturned because Jacques Alexys Romao was ruled to be ineligible.