The 1982 United Nations Convention on the Law of the Sea (UNCLOS) is widely viewed as a ‘constitutive’ instrument that provides a legal framework that is being filled in, rounded out and complemented by existing and subsequently enacted international agreements and customary international law. The International Maritime Organization (IMO) is the preeminent international organization with competence to establish international rules and standards for the safety, security and environmental performance of international shipping. In other words, on matters relating to international shipping, UNCLOS outlines the rights and obligations of States parties in various maritime zones that must be exercised and fulfilled through implementation instruments under the auspices of IMO. This article will examine and discuss the relationship between UNCLOS and IMO instruments, in particular the role of IMO and its instruments in assisting States to exercise their rights and fulfil their obligations under UNCLOS.