The dynamics of the relationship between political participation and legitimacy have received limited attention, despite the widely held view that the former contributes to the latter. This article advances conceptualizations of this relationship by demonstrating how participatory innovations can be analysed as processes of legitimation. Studies of participation highlight how institutional actors define the terms of participation, but do not attend to how these terms function in constructing legitimacy. Studies of legitimation, conversely, emphasize participation but pay limited attention to how participatory innovations form. Building on these linkages, the article describes how the modes of participation framework can be used to evaluate the legitimating potential of participatory innovations and demonstrates this in the case of the Association of Southeast Asian Nations Civil Society Conference. The article demonstrates that more participation does not necessarily increase legitimacy, and calls for greater attention to what is being legitimated and to whom through participatory innovations.