Global sustainability targets demand transformative changes. Nature-based solutions (NbS) are gaining traction in science and policy, but their potential for transformative change remains unexplored. We provide a framework to evaluate how NbS contribute to transformative change and apply it to 93 NbS from mountain social-ecological systems (SES). The framework serves to assess what elements may catalyze transformative change, how transformative change occurs, and what its outcomes are. Our results show that NbS are as much “people based” as “nature based.” Most NbS are based on four elements with transformation potential: nature's values, knowledge types, community engagement, and nature management practices. Our results confirm the potential of NbS for transformative change, observed through changes in non-sustainable trajectories of SES. We illustrate the components of our framework through a novel classification of NbS. The framework provides key components for assessing the effectiveness of NbS and allows tracking long-term transformative change processes.