The Annex VII Tribunal Awards in the jurisdiction and merits phases of the South China Sea Arbitration dealt with the maritime jurisdiction of various features in one of the world’s most contested regions of the world. Five different states lay claim to features in the South China Sea, as well as a claim and occupation of an island by Taiwan. It is long established in international law that if the rights of a third party are in issue within a dispute, then that party has a right of participation in the proceedings, or alternatively that a tribunal will not have jurisdiction to deal with the rights of the third party. In the South China Sea Arbitration, the Tribunal chose to deal with the potential maritime jurisdiction of features of other states, and not to apply the indispensable third party rule to restrict its award. This chapter looks at the application of the indispensable third party rule by the Tribunal, and what the implications of the decision might be in future cases.