Biographical data of terrorists and overlapping theories indicate that ostracism has the power to promote a terroristic mindset. This effect, however, has not been investigated empirically so far. The current studies aimed to fill this research gap and test this relationship experimentally. Inclusionary status was manipulated in an online and a lab study. To assess how far participants would go on behalf of a terrorist group, participants were introduced to a pro-democracy and animal protection terrorist organization, and asked for their degree of agreement to their actions. Study 1 showed that ostracized participants always favored more extreme options to support a terrorist group compared to participants in an inclusion or a neutral control condition, which grew from non-violent means to property damage. In Study 2, ostracism increased the willingness to destroy property on behalf of a terrorist group. Indicating an underlying mechanism, this effect was mediated by a low sense of control. The findings are consistent with theoretical and empirical work of both ostracism and terrorism research, and provide one of few pieces of experimental work to illustrate a root of radicalization.