Investment arbitration usually has its legal basis in the bilateral investment treaty (BIT), regional or multilateral treaties or in an investment contract. Some treaties cover only disputes relating to obligations under these kinds of agreements, i. e. only for claims of treaty violations. Some others create an international law obligation, according to which the host state shall observe any binding obligation with respect to investments. These and other similar provisions are commonly called “ umbrella clause” . Although other formulations have also been used, Clauses of this kind have been put into treaties to provide additional protection to investor and are directed for covering investment agreements that host countries frequently conclude with foreign investors. In most of the investment treaties, the umbrella clauses are not always with the same wording, so arbitral tribunals have given different interpretations and reached conflicting conclusions. This study gives an overview of the origin and significance of the wording of this Clause in BITs, then looks at the effect, scope, and conditions of application of the Clause as interpreted by ICSID arbitral tribunals and tries to analyze ICSID arbitral jurisprudence on the basis of restrictive or extensive interpretation of the Clause.