This thesis aims at an analysis of the interpretation and application of denial-of-benefits clauses in international investment arbitration, with a specific emphasis on energy investment disputes. In such elaboration, it, first, covers the definition, purpose, scope, and boundaries of the denial of benefits in conceptual terms. Second, it examines the evolution of such clauses in terms of their components and types. Thereafter, whether the relevant rights are of jurisdictional or admissibility nature, the substantive and procedural requirements included in such clauses, whether the invocation of DOB rights has a prospective or retrospective effect, and the burden of proof regarding the fulfillment of denial-of-benefits requirements are addressed. At the end, considering the allegedly problematic application of the so-called denial-of-benefits clause in the Energy Charter Treaty, Article 17, the modernization process of the Energy Charter Treaty is examined.