Adequately responding to the crisis of marine plastic pollution will require parallel actions, by a variety of actors, on multiple fronts. The ocean governance regime, which has generally failed at shaping state behavior around land-based pollution, offers important legal and conceptual resources that can and should be utilized in these efforts. This article reviews three areas where the United Nations Convention on the Law of the Sea (UNCLOS) could be activated or applied to the problem of marine plastic pollution: the common heritage of mankind principle, the dispute settlement system, and reform through implementing agreements. Utilizing these elements of the ocean governance regime would be complementary to on-going efforts to negotiate a new plastics treaty. Working through UNCLOS offers several advantages, including important in-roads for non-state actors, norm-strengthening through an already well-subscribed regime, and expanding the avenues and obligations for scientific data collection on the patterns and impacts of marine plastics.