Transnational private institutions (TPIs) navigate the tension between expert and participatory demands, balancing technocratic and democratic values in their legitimation strategies. How can we study this tension, and why might TPIs favor either technocratic or democratic legitimation? This paper examines these questions through a case study of the International Organization for Standardization’s (ISO) portfolio expansion. Expanding on earlier frameworks of legitimation strategies among TPIs, this study investigates whether regulating societal issue areas influences ISO’s legitimation strategies. Drawing on a novel dataset, the findings reveal that in contrast to the traditional physical standards, ISO uses democratic legitimation strategies for societal standards in both the input and output phases of the process. This highlights the utility of an expanded conceptualization when examining the legitimation strategies of TPIs, particularly as they increasingly engage in the regulation of societal issues.