ABSTRACT While previous studies have mainly emphasised the role of structural factors in explaining how and why Chinese environmental NGOs (ENGOs) have become more engaged in policy advocacy since the early 2000s, this study offers an alternative perspective on these dynamics by adopting an organisational learning framework. Through in-depth case studies, we identify the production and application of knowledge – specifically regarding the significance, viability, and practical expertise of policy advocacy – as a pivotal driver that compels organisations to proactively engage in policy advocacy. Moreover, we delineate two primary approaches to organisational learning used by ENGOs – intra-organisational learning and trans-organisational learning – and illustrate their internal mechanisms. This study also underscores the significance of individual learning by organisational leaders in the Chinese context, which occurs in parallel with collective learning at the group level. This article thereby enriches our understanding of the trajectory of environmental activism in contemporary China.