With the passing of several UN Security Council Resolutions related to Women, Peace and Security, gender balancing security sector reforms (SSR)—or policies that ensure the equal participation of women in the security sector—have received increased global attention over the past two decades. However, to date, there is no explanation for variation in their adoption. This paper examines the internationalization of SSR gender reform, arguing that the presence of a peacekeeping mission within a post-conflict country affects the state’s resources and political will to adopt gender balancing reforms. We explore the effect of multidimensional peacekeeping using an original dataset on SSR in post-conflict countries, the Security Sector Reform Dataset, from 1989 to 2012. We find that peacekeeping missions increase the probability that a state will adopt gender balancing reforms in SSR. As the first cross-national quantitative examination of gender balancing reforms, these findings also shed light on the conditions under which states adopt security sector reforms more generally.