The Article demonstrates the understanding of the concept of Fair and Equitable Treatment (FET) in foreign investment. This Article examines the vagueness in FET standard which is the core problem that creates a precarious position for Transnational Corporation and Host State in its operation. This Article points alert the meaning of Fair and Equitable Treatment’ in context of international investment law and examine the relationship of Fair and Equitable Treatment and Customary International Law, with pinpointed by analysing international and judicial and arbitral cases that will assist in coming out of precarious penumbra encircled to the concept of FET; host state and investor role in deciding the scope of FET and recent surge in case- law as to investor-state disputes. This Article suggest possible solution and balancing approach to come out of the penumbra created due to excessive interpretation, for the private foreign investor and Host State.