The rock-dwelling cichlids from Lake Mala?i comprise a diverse group of haplochromine fishes within 14 genera. Within Petrotilapia, there are three species groups; a new species of Petrotilapia in the P. nigra group from Mumbo Island, Lake Malawi is described herein. Three Petrotilapia species are known to occur at Mumbo Island: P. mumboensis, P. nigra, and the new species. Males of the new species are distinguished by gold coloration in the cheek, and gular regions.