Research into violent extremism is lacking integrated theoretical frameworks explaining individual involvement in politically or religiously motivated violence, resulting in a poor understanding of causal mechanisms. Building on situational action theory, the current study moves beyond the dominant risk factor approach and proposes an integrated model for the explanation of political/religious violence, distinguishing between direct mechanisms and “causes of the causes.” The model integrates mechanisms from different but complementary traditions. Following previous work, this study focusses on the causes of the causes influencing direct key mechanisms, violent extremist propensity, and exposure to violent extremist moral settings that explain political/religious violence. The theoretical model is tested using structural equation modelling. The analyses are based on a web survey (N = 6,020) among adolescents and young adults in Belgium. Results show that violent extremist propensity and exposure to violent extremist moral settings have direct effects on the likelihood of political/religious violence. These direct mechanisms are in turn determined by a series of exogenous factors: perceived injustice and poor social integration. The relationship between perceived injustice and poor social integration and political/religious violence is further mediated by perceived alienation, perceived procedural justice, and religious authoritarianism. The implications of these findings are discussed.