This chapter focuses on studying the evolving trends in the investment treaty practice on two core non-discrimination standards in international investment law: the most-favoured nation (MFN) and national treatment (NT) standards. Before discussing these two standards, it is pertinent to mention that the term ‘non-discrimination’ in an investment treaty may exist in multiple places. For example, several treaties forbid states from adopting arbitrary or discriminatory measures. Likewise, BITs routinely mandate states to follow the principles of non discrimination while lawfully expropriating investment. The focus of this chapter is restricted to the two core non discrimination standards. Much as in the case with trade law, these two non-discrimination standards are relative or comparative; that is, their effectiveness is contingent on the level of treatment the host state provides to other foreign (in the case of the MFN standard) and domestic (in the case of NT) investors. Accordingly, these investment protection standards differ from standards like fair and equitable treatment and full protection and security, which are absolute. The chapter first discusses the MFN standard followed by the NT clause.