Effective monitoring, control and surveillance (MCS) is critical for the success of marine conservation and management measures. Whereas States have the exclusive right to manage the marine resources within their national jurisdiction, areas beyond national jurisdiction (ABNJ) are subject to a complex patchwork of international rules and regulations. Effective MCS of these deep and distant waters is a significant technical challenge and there is growing interest in how MCS tools and policies can be applied to this vast global commons. States at the United Nations (UN) are currently negotiating an international legally binding instrument (ILBI) for the conservation and sustainable use of the biological diversity of marine areas beyond national jurisdiction (referred to here as the “high seas treaty”). This brief explores how the negotiations could strengthen MCS in ABNJ and the contribution MCS could make to the implementation of a future treaty.