This paper explores ideological change within violent sub-state actors, specifically focusing on the processes through which groups become more secular or more religious. Challenging existing depictions of such groups as possessing static and unchanging “secular” or “religious” ideologies, it answers the following questions: How and why do violent groups and sub-state actors undergo processes of religionization / secularization? What factors promote or forestall such changes, and why do some factors have more influence than others? Despite extensive research which has analyzed differences between secular and religious terrorism and political violence, studies have tended to treat actors as following a monolithic worldview, essentializing groups as being statically “secular” or “religious” in order to analyze differences among them. Furthermore, while such groups holding religious agendas have been shown to be deadlier and broadly more violent compared to secular groups, the process whereby groups become religious (or secular) has remained surprisingly understudied. Recognizing that over time religiosity – just like any other ideological construct – may be adopted to greater or lesser extents within a group’s worldview, I draw on social movement theory’s frame analysis in order to disaggregate groups’ ideologies into more nuanced components, analyzing how conflict dynamics influence variations in the relative dominance religion has within the groups’ ideological position. Conducting a process-based paired comparison of the Palestine Liberation Organization (PLO) and the Palestinian Hamas, I analyze the communiques and leaflets each group disseminated throughout the six-year period of the First Intifada, tracing religionization / secularization processes each group underwent in response to shifts in Israeli repression, international / regional certification, internal competition among groups, and regional political realignments. The results demonstrate that group religiosity should be understood as a dynamic rather than static construct, increasing and decreasing within groups' perceptions in response to emerging political change. Furthermore, and somewhat contrary to expectations, the more religiously-inclined Hamas showed higher sensitivity to emerging conflict developments, shifting more extensively between secular and religious perceptions compared the secularly-inclined PLO. The paper concludes by exploring the applicability of these findings, extrapolating them further and suggesting avenues for future development and policy-related analyses.