While scholarship on the topic of gender and the environment is steadily growing, little is known about the challenges faced and successes seen by women and gender NGOs operating as a central part of environment-focused civil society. In this paper, I offer such an analysis, examining the political strategies-rhetorical and procedural-mobilised by the Women and Gender Constituency (WGC) in the United Nations Framework Convention on Climate Change (UNFCCC). I argue that the WGC has seen lots of success in mobilising arguments that foreground women's vulnerability to the effects of climate change. But at the same time, the constituency has seen far more resistance to more intersectional feminist arguments that interrogate the role of masculinised discursive power in shaping climate politics. This is at least in part a result of a wider structure of civil society that pigeonholes different identities (e.g. gender, youth, indigenous peoples) in a way that separates their deeply interconnected struggles. Understanding this structural barrier, or dark side of civil society, is crucial to envisioning a more fruitful integration of civil society in sustainability politics.