The body is counter-shaded, with bluish black dorsal surface, snout and tail and a white belly and throat underneath. Blazes of gray run along the flanks. Duskies have a short stubby beak, much different from the prominent beaks of the stenellid species. The tall and slightly hooked dorsal fin is darkly colored on the leading edge but fades to lighter gray towards the trailing edge.
Flippers are pale gray in front but darken in color along the trailing edge.
The body shape is small and moderately chunky. Maximum reported length for African specimens is 1.93 m for females and 1.81 m for males. Adult weights range from 40 to 80 kg, though birth weight is not known for the African population. Reported birth length ranges from 55 to 70 cm in other areas. African specimens tend to be larger than specimens from New Zealand, but smaller than those from Peru.