ABSTRACT Religious engagement can foster either democratic or illiberal views among adherents. Some religious institutions attempt to mobilize believers against abortion rights. For these believers, when does religion mobilize pro-choice protest participation? I test three pathways by which a prescriptive norm of pro-life protest participation might mobilize believers: general religiosity, hierarchical pressure from religious leaders, and pressure from fellow parishioners. Using semi-structured interviews with Polish anti-abortion organizers and an original, pre-registered survey experiment of Polish Catholics, I show that religiosity does not mobilize anti-abortion activism. Instead, religious group engagement powerfully drives pro-life protest. Hierarchical pressures from religious leaders and group pressures from fellow parishioners only increase the likelihood that believers protest against abortion for highly engaged parishioners, but not less-engaged parishioners. Further, religious group engagement levels fully mediate these relationships. Thus, hierarchical and social norms impact individuals’ protest propensity to the extent that they are deeply embedded in a tightly knit social group.