How do religious civil wars evolve? Many violent conflicts are fought between groups of different faiths. The paper argues, however, that religious differences rarely directly lead to conflict onset. Rather, the apparent religious dimension of many civil wars is a consequence of successful religious framing. Political and military leaders offer religious interpretations designed to legitimize the use of force and to mobilize believers to violent action. Such framing processes can be more or less successful, depending inter alia on the authority of the political and religious leadership, on the coherence and appropriateness of the frames, on the existence of persuasive counter-frames, and on the availability of communication infrastructures that allow for effective dissemination of religious frames. Comparing violent conflicts in the Philippines and Thailand, the paper shows that religious mobilization can fail along the theoretically predicted lines.