This paper examines which factors influence women’s descriptive representation in state delegations to the international climate change negotiations. Due to the gendered nature of climate change as an issue, it is important to study the representation of women in the negotiations and to examine its normative and functional implications. Theoretically, I propose to look at institutional, socioeconomic, and cultural factors as potential explanations for the variation in the proportion of women in state delegations across countries. I examine this variation by drawing on a dataset containing all member state delegations to the United Nations Framework Convention on Climate Change negotiations from 1995 to 2011. The theoretical arguments are then tested on these data using a fractional probit model. This is the first comparative study of women’s descriptive representation in international environmental negotiations. It contributes to our understanding of the variation in women’s representation both over time and across countries. In particular, I find that women’s representation is higher in countries that enjoy a higher level of development and a higher degree of political gender equality. The effects of other institutional and socioeconomic factors such as the level of democracy or gender-equal development remain statistically insignificant. Cultural factors measured by regional proxies show that Eastern Europe and Latin America are positively and the Middle East negatively linked with women’s descriptive representation in delegations.