The conclusion of the Convention on the Legal Status of the Caspian Sea in 2018 was intended to put an end to a very long and difficult negotiation process to determine the legal regime for this closed water body, which has no natural connection with the World Ocean. The Convention was supposed to fill the gaps in the management of this water area that existed in the framework of the previous Soviet-Iranian agreements of 1921 and 1940, which were in force but not up to date, and to give all the Caspian states common and equal rights and powers to use and exploit the spaces and resources of this maritime region. However, up to 2022, the Convention has not entered into legal force, as one of the Caspian countries - the Islamic Republic of Iran - has not yet ratified this regional agreement, considering that it is the most disadvantaged party. Despite the resolution of the Caspian Sea seabed delimitation issues in its northern part in previous years, the problem of delimitation in its southern part may require both enormous efforts and time, further complicating the current situation. There is as yet no final understanding as to what delimitation models can be used here to satisfy the interests of all the states involved. Moreover, the implementation of the norms and provisions of the 2018 Convention requires the drafting and signing of new bilateral and multilateral documents that close a whole series of “gaps” in the proposed convention regime. In fact, the fate of the 2018 Convention depends on how these contradictions will be resolved. The analysis of these problems is the focus of this paper.