Diagnosis: A large, deep-bodied species with a steep head profile, narrow head and small mouth; often appearing brownish with a white belly, some individuals have bright red bellies (Ref. 118638). The sexes look very similar, although males are usually larger (Ref. 118638). Very difficult to distinguish from Coptodon zillii, but C. rendalli usually have a steeper head profile and less prominent vertical bars; in East Africa, the tailfin of C. rendalli is often divided into a brownish upper part and yellowish lower part, whereas that of C. zillii is uniform and spotted (Ref. 118638).

Description: moderately deep-bodied, ovoid shaped; head relatively short; mouth small (Ref. 52307).

Colouration: head and body mid to dark olive-green dorsally, paling over the flanks (Ref. 4967, 34290). Body usually with vertical bars only (Ref. 4967, 34290), 6-8 on head and body (Ref. 52307). Scales with a dark basal crescent (Ref. 4967, 34290, 52307). Dorsal fin olive-green with a thin red margin and white to grey dark oblique spots on the soft rays; caudal fin spotted on dorsal half and red or yellow on ventral half (Ref. 4967, 34290). Lower lips, throat, lower parts of cheeks and opercles, breast and belly, as well as some lower parts of caudal peduncle, light to deep red (depending on behavioral situation) in most, but not all populations; anal fin reddish (Ref. 52307).