Actors involved in the construction of a transnational standard in the field of corporate responsibility (csr) perform different types of institutional work in order to succeed with their project. This research focuses on processes and actors and compares the initiation of two standards : the un Global Compact and iso 26000. Our research sheds light on the link between types of institutional work and dimensions of legitimacy. This fosters our understanding of legitimation mechanisms in the initial phase of a standardization project. Our analysis reveals that institutional work is paramount in the early construction of a standard and that it can take different forms depending on the specific circumstances of the cases in question.