The diet of F. oustaleti includes invertebrates such as large insects as well as some vertebrates such as small birds and reptiles. This is also one of several chameleon species that are known to consume fruit. F. oustaleti is known to regularly consume the fruit of Grangeria porosa, Chassalia princei, and Malleastrum gracile, and will do so even during the wet season, suggesting that fruit is not consumed just to obtain water.
The diet of F. oustaleti comprises invertebrates such as large insects, along with some vertebrates like small birds and reptiles. This is also one of several chameleon species that consume fruit. F. oustaleti regularly consumes the fruit of Grangeria porosa, Chassalia princei, and Malleastrum gracile, even during the wet season, indicating that fruit is not consumed solely for water.