This article investigates the effect of dispute settlement decisions under the 1982 United Nations Convention on the Law of the Sea (UNCLOS) and whether and how states, particularly great powers, comply with these decisions. State practice suggests that an overwhelming majority of the decisions by UNCLOS dispute settlement bodies have been implemented. Significantly, not only small states but also the permanent members of the United Nations Security Council have complied with UNCLOS dispute settlement decisions even when they ‘lost’ in the proceedings that were unilaterally initiated against them.