<p>Amid growing climate risks, the climate litigation provides a legal weapon for social actors to defend their rights. NGOs, due to their autonomy and professionalism, play an important role in organizing climate litigation and have gained scholarly attention. However, existing explanations often focus on structural or legal opportunity factors, overlooking how NGOs themselves shape litigation outcomes through strategic engagement. To address this gap, this paper applies the Most-Similar-Systems Design (MSSD) and an Actor-centered Institutionalism (ACI) framework to examine two climate lawsuits initiated by the same Chinese NGO—Friends of Nature—within comparable legal and political settings. Despite similar contexts, the two cases diverged significantly: one stalled due to procedural rigidity, while the other achieved a mediated resolution with substantial policy impact. The findings demonstrate that the key to success lies not in legal frameworks alone, but in the NGO’s capacity to adapt to institutional constraints, align with policy narratives, and engage constructively with courts and regulators. By foregrounding agency within institutional interaction, this research offers a more dynamic understanding of how NGOs can navigate semi-authoritarian systems and exert meaningful influence in climate governance.</p>