The aim of this chapter is to examine the role of the United Nations (UN) in treaty-making in the field of the law of the sea. In particular, this chapter addresses the First and Third United Nations Conferences on the Law of the Sea, and the treaty-making process of two implementation agreements, that is, the 1994 Implementation Agreement and the 1995 Fish Stocks Agreement. In this regard, it is important to note that the tasks of the conferences in the field of the law of the sea have changed over time. At the First UN Conference on the Law of the Sea, its primary task was to establish a legal framework for coordinating interests of individual states according to multiple jurisdictional zones. In contrast, the Third UN Conference on the Law of the Sea that adopted the UN Convention on the Law of the Sea (UNCLOS) dealt not only with the reconciliation of competing state interests but also with the safeguarding of community interests, such as the establishment of the deep seabed regime on the basis of the principle of common heritage of mankind and marine environmental protection. As demonstrated by this Conference, the task of treaty-making conferences under the auspices of the UN is no longer limited to the reconciliation of state interests but includes the safeguard and promotion of community interests at sea. Thus, the reconciliation between state interests and community interests should be a crucial issue in treaty-making in the law of the sea.