This hyperoliid was found in a forested area 2 km south of Mbalangi in the Fako District of southwestern Cameroon together with a Leptopelis boulengeri, Amietophrynus tuberosus, and a Charina (Calabaria) reinhardtii.
Opisthothylax immaculatus is a species of frog in the Hyperoliidae family. It is monotypic within the genus Opisthothylax. It is found in Cameroon, Democratic Republic of the Congo, Equatorial Guinea, Gabon, Nigeria, possibly Angola, possibly Central African Republic, and possibly Republic of the Congo. Its natural habitats are subtropical or tropical moist lowland forests and rivers. It is threatened by habitat loss.