This paper conceptualizes standardization as institutional work to study the emergence of a standard and the deployment of its regulatory power. We rely on unique access to longitudinal archival data for exploring how the FTSE4Good index, a responsible investment index, emerged as a standard for socially responsible corporate behavior. Our results show how three types of standardization work - calculative framing, engaging and valorizing - support the design, legitimation and monitoring processes whereby a standard acquires its regulatory power. Our findings reveal new facets in the dynamics of standardization by approaching standardization as a product of institutional work and in showing how unintended consequences of that work can be recaptured to strengthen the regulatory power of the standard