In this study I explore how security sector reform affects the likelihood of democratization after a nonviolent resistance campaign in order to better understand the role of core security services during regime changes and the mechanisms of SSR. By using literature on nonviolence resistance, security sector reform, and by borrowing the concept ofspoilersfrom policy and peace-making literature, I hypothesise that SSR will likely increase the ability of core security actors to manage security problems in the transition after a nonviolent resistance campaign, as well as reduce spoiler capabilities among core security actors, thereby increasing the probability of democratization.I used the method of structured, focused comparison on the regime changes in Tunisia 2011-2014 and Egypt 2011-2013, and found some evidence contrary to the first, while limited support for the second.