Isla de los Estados hosts few native mammal species: the South American Fur Seal, the South American Sea Lion, the Southern Elephant Seal, the Southern River Otter, the Marine Otter (of uncertain presence), and the Olive Soft-haired Mouse. Indigenous people reaching sporadically the island utilized the pinnipeds, but the sealing occurring between the eighteenth and the twentieth century depleted seal numbers severely. At the same time, otters might have been hunted by sealers and sailors for their fur. Today, pinnipeds at Isla de los Estados are recovering. The last survey of 2012 reported ~9500 South American Fur Seals, increasing at a rate of 6.4%/year since 1995. The South American Sea Lion reached ~900 individuals, increasing at a rate of 8%/year since 1997. Southern Elephant Seals, on the other hand, could be developing a new breeding location. The Southern River Otter shows a stable presence and reproduction, but their main threat is habitat degradation from trampling by introduced Red Deer and Goats. The native mice may face threats from the introduced rat species. Although pinnipeds are currently protected at the island, the impact of fisheries around the archipelago remain poorly understood. The island’s isolation helped in the recovery of the mammal species after their exploitation but contributed to the impact by uncontrolled introduced species. Its isolation also poses difficulties for scientific research and management.