The Southern Ocean's areas beyond national jurisdiction (ABNJ) are uncommon in a number of ways. This article first discusses features of the Southern Ocean's uncommonness that may be relevant to the relationship between the Antarctic Treaty System (ATS) and the development of the international legally binding instrument on the conservation and sustainable use of marine biological diversity of ABNJ under United Nations General Assembly Resolution 69/292 (ILBI). Second, the article considers the potential relationship between the ILBI and the ATS. Third, the article discusses the current approach of the ATS to governance of the Southern Ocean's ABNJ by focusing on two particular topics which are to be included in the development of the ILBI. The topics discussed are measures (such as area-based management, including marine protected areas) and marine genetic resources.