The dolphin's range is patchy, with major populations around South America, southwestern Africa, New Zealand, and various oceanic islands, with some sightings around southern Australia and Tasmania.

The dusky dolphin was described as Delphinus obscurus by John Edward Gray in 1828 from stuffed skins with skulls shipped from the Cape of Good Hope to the British Museum in 1827.

[3][4] However, Gray later wrote that a similar dolphin was described as Delphinus superciliosus by French surgeons and naturalists René Lesson and Prosper Garnot in 1826 based on a specimen near Tasmania.

[22] Off South America, they range from southern Peru to Cape Horn in the west and then up to around 36°S in the east, along with the Falkland Islands.

[15] Within Australian waters, dusky dolphins have been recorded off Kangaroo Island, eastern Tasmania, and in the Bass Strait,[24] although they are uncommon and may be transients from New Zealand.

They largely live in inshore waters and can be found up to the outer continental shelf and in similar zones in offshore islands.

[15] Around Kaikōura, New Zealand, the majority of individuals were seen only once in the area over the course of 30 years, suggesting a high occurrence of immigration and emigration.

[15] Most studies of foraging and social behaviour in the species have occurred at Kaikōura, Admiralty Bay and San Jorge Gulf, Argentina.

[29][30] Dusky dolphins live in a fission–fusion society, where individuals move in and out of groups depending on social and ecological conditions.

They also associate with various seabirds, such as kelp gulls, cormorants, terns, shearwaters, petrels, albatrosses and Magellanic penguins.

Common fish species eaten include anchovies, lantern fish, pilchards, sculpins, hakes, horse mackerel, hoki and red cod, while squids preyed on include those of the genera Nototodarus, Todarodes and Loligo.

[15] Dusky dolphins are generally coordinated hunters and their flexible foraging strategies can change depending on the environment.

The number of dolphins in these groups ranges up to five members and decrease down to single individuals as the layer descends.

[43] In San Jorge Gulf and Admiralty Bay, dusky dolphins herd schools of fish into bait balls during the day.

[44] In San Jorge Gulf, bait herding occurs from October to January,[32][36] while at Admiralty Bay, it takes place from August to November.

Females seem to prefer males with great speed and agility over size, strength, or aggression.

[47]: 167–169  Off Kaikōura, dusky dolphins have been found to contain scars and notches on their dorsal fins that are suggested to be caused by fighting over mates,[49] however, one study in the same area did not observe male dusky dolphins in mating groups fighting amongst themselves nor controlling who can be part of the group, but did record interferences of copulations.

[47]: 170  As with other species where females mate with multiple partners, male dusky dolphins have large testes for sperm competition.

[4] Calves are born during the spring (August to October) off Peru, and in summer (November to February) off Argentina, South Africa and New Zealand.

[4] Dusky dolphins perform a number of aerial displays, which are classed into noisy, clean, acrobatic and coordinated.

Noisy leaps end in splashes upon re-entry and include backslaps, headslaps, sideslaps, tailslaps and belly flops.

Acrobatic leaps are complex and consist of head-over-tail flips or somersaults and spins, both of which can cause splashes.

[45]: 67 [54][55] Off Peru, parasites include those of the genera Nasitrema and Anisakis, and Phyllobothrium delphini, Braunina cordiformis, and Pholeter gasterophilus.

[54] One study of dolphins off Patagonia found that the most common parasites were Anisakis simplex, Braunina cordiformis and species of the genus Hadwenius.

[56] Dusky dolphin watching is also popular in New Zealand, whose dolphin-watching industry started in the late 1980s as a side attraction to sperm whales.

Attractions include viewing and swimming with dusky dolphins, notably in Kaikōura and Marlborough Sounds.

Dolphins may lose energy interacting with or avoiding vessels—energy they could use for socialising and feeding— and they appear to spend more time resting when the boats are around.

The larger and more nocturnal foraging groups of dusky dolphins in New Zealand also leads to less encounters with vessels.

Although information is sparse, several Dusky Dolphin populations are large, seemingly stable, and not subject to high levels of anthropogenic threats".

[65] Dusky dolphins may fall victim to the illegal small cetacean fisheries of Peru and Chile.