Biodiversity beyond national jurisdiction (BBNJ) is facing an ever-increasing and emerging list of anthropogenic pressures. As the long-term protection of BBNJ is a shared issue that transcends the boundaries of a single State, collective action is required in response. However, cooperation has been the Achilles heel of the existing international law framework for marine areas beyond national jurisdiction (ABNJ). To date, ABNJ have been governed by a complex patchwork of global, regional, and sectoral organizations and bodies, each with their own mandates and priorities. While the 1982 United Nations Convention on the Law of the Sea played an important role in consolidating principles that inform effective ocean governance, including cooperation, the legal contours of the duty to cooperate were not precisely defined in the Convention, and it lacks cooperative mechanisms to ensure coordination between existing governance regimes with competences in ABNJ. On 19 June 2023, member States of the United Nations adopted, by consensus, the Agreement Under the United Nations Convention on the Law of the Sea on the Conservation and Sustainable Use of Marine Biological Diversity of Areas Beyond National Jurisdiction (BBNJ Agreement). As the BBNJ Agreement marks the dawn of a new era in oceans governance and represents another development in the institutionalization of international cooperation, this chapter explores the instrument’s framework for cooperation and the specific mechanisms and techniques it utilizes to strengthen, enhance, and foster coordination, coherence, and harmonization between and among States and existing governance organizations and bodies to ensure ocean health in ABNJ.