Commerson's dolphins are found in cold inshore waters along open coasts, in sheltered fjords, bays, harbours and river mouths, and occasionally the lower reaches of rivers. Their offshore limit is not very clear. Along the Atlantic shelf Commerson’s dolphins have been sighted more than 100 nmi offshore and in water deeper than 1000 m (Pedraza 2008). Within the Strait of Magellan, they prefer the areas with strongest currents, such as the Primera and Segunda Angostura (First and Second Narrows), where the current can reach or exceed 15 km/hr (Goodall 1994). Off South America, Commerson's dolphins appear to prefer areas where the continental shelf is wide and flat, the tidal range is great, and temperatures are influenced by the cool Malvinas Current. In coastal Patagonia, they are found principally in areas with continental runoff such as at the mouths of the Chubut and Santa Cruz Rivers and at Puerto Deseado. Around the Falklands/Malvinas and Kerguelen Islands, as well as off mainland Argentina, they are often seen swimming in or at the edge of kelp beds. Commerson's dolphins sometimes move very close to shore, even inside the breakers. However, they are also observed offshore in waters deeper than 50 m.

South American Commerson's dolphins appear to be opportunistic, feeding near the bottom on various species of fish, cephalopods, crustaceans, and benthic invertebrates in kelp beds but also on pelagic schooling fish in more open areas. In the Kerguelen Islands, they seem to have a more restricted diet, consisting mostly of fish.