South American Sea Lions are widely-distributed, occurring more or less continuously from northern Peru south to Cape Horn, and north up the east coast of the continent to southern Brazil. They also occur in the Falkland/Malvinas Islands. The northernmost breeding distribution on the Pacific side is Isla Lobos de Tierra (6º26’S; Peru). No breeding colonies occur in Brazil. The northernmost breeding rookery in the Atlantic is Isla de Lobos, on the Uruguayan coast.

South American Sea Lions are primarily a coastal species, found in waters over the continental shelf and slope; they occur only infrequently in deeper waters. This species ventures into fresh water and can be found around tidewater glaciers and up rivers. Vagrants have been found as far north as 13°S, near Bahia Brazil and in the Galápagos Archipelago (Ecuador).