Oeno Atoll measures about 5 kilometres (3.1 mi) in diameter, including the central lagoon, with a total area exceeding 20 square kilometres (7.7 sq mi).

Their aggregate land area is only 0.69 square kilometres (170 acres).

Oeno serves as a private holiday site for the few residents of Pitcairn Island, who travel there and stay for two weeks in January because Oeno has beaches while Pitcairn doesn't.

Three smaller islets are to the south and west of the main island.

The island has been identified by BirdLife International as an Important Bird Area (IBA) principally for its colony of Murphy's petrels, which, at some 12,500 pairs, is estimated to be the second largest colony of these birds in the world.