We describe a new species of Acanthixalus from southwestern Ivory Coast. Acanthixalus sonjae sp. nov. differs from the Central African Acanthixalus spinosus genetically by 4.6 % in the investigated 16S rRNA. Morphologically adult frogs are very similar to A. spinosus. Male A. sonjae have wider heads and probably smaller gular glands than A. spinosus. Tadpoles of A. sonjae differ by much longer tails. Acanthixalus sonjae males are apparently mute. The new species is semiaquatic and lives in large water-filled cavities of trees in secondary and primary rain forest. Tadpoles complete metamorphosis in three months. They are at least partly carnivorous.