There is a novel practice of incorporating corporate social responsibility (CSR) provisions into international investment agreements (IIAs) that distinguish them from previously observed clauses pertaining to environmental and human rights. The chapter examines the legal nature and situation of CSR provisions in the investment regime. Based on an empirical analysis of existing IIAs with CSR language, the majority of CSR clauses found are classified as soft law due to their non-binding and advocacy-oriented language. However, certain countries have introduced stricter and more concrete requirements in their treaties. Additionally, reforms have been observed in dispute settlement clauses, including the establishment of joint administrative committees and the inclusion of CSR issues in arbitration or counterclaims. This ongoing reform increases the degree of legalisation of CSR requirements. The research identifies six typical party-based model provisions. These countries or regions include the EU, Canada, Brazil, Colombia, India, and Argentina. Referring to Kenneth W Abbott’s legalisation theory, the present chapter makes a horizontal comparison measuring these six model provisions. The measurement of the legalisation of CSR clauses helps to explain why and how such CSR clauses come into being with the advocation of certain groups of countries and the potential development of promoting CSR provisions.