The last half-a-century has seen a marked demand for authentic citizen participation in public policy-and decision-making, not least in the field of sustainability. The depth and forms of citizen engagement in nature-based solutions (NBS), for example, and how such participation shapes their trajectories is gaining increasing attention. In this paper, we analyze current forms and implications of citizen participation in 58 NBS case studies conducted in 21 cities in the light of supporting wider sustainability goals. Our results show that while tokenistic forms dominate citizen participation across a variety of NBS contexts, collaborative multi-stakeholder forms of engagement do not automatically lead to enhanced ecological functions. Deeper forms of engagement, however, strengthen and diversify both expected and unexpected social outcomes, including social learning, enhanced sense of belonging, environmental stewardship, and inclusiveness and equity, in general. Driven by neoliberal austerity logic governments often cede power to NBS promoters whose interests predefine an intervention's vision of nature. Deeper levels of participation are hence limited by inherent institutional structures, neoliberal regimes and the lack of trust among actors involved. These limitations can be partially bridged by strengthening relational and reflexive capacities of public institutions. Focusing on the process of citizen engagement and creating multiple arenas for discussion could bring out new voices and narratives and also transform the culture of participation.