This study investigates the role of Disintegration—a personality trait marked by cognitive-perceptual disturbances and reality distortion—in predicting the Militant Extremist Mind-Set (MEM) among both general and extremist populations in Indonesia. In Study 1, involving a community sample (N = 282), Disintegration significantly predicted all three MEM components (Proviolence, Vile World, and Divine Power), with structural equation modeling indicating full mediation between disintegration and radical intentions via MEM. Study 2 examined actual extremists (N = 141), including in-prison and out-prison terrorists, and found that disintegration remained a robust predictor of MEM, especially its God component. Notably, out-prison extremists scored highest on ideological justification for violence, while in-prison extremists showed lower MEM and disintegration levels, suggesting contextual modulation of militant cognitions. The findings contribute to radicalization theory by highlighting disintegration as a dispositional vulnerability that intensifies cognitive-emotional commitment to extremist ideologies. Theoretical implications are discussed in relation to closed-mindedness, apophenia, and psychosis-proneness. Practical recommendations include integrating cognitive-behavioral strategies into deradicalization efforts and tailoring interventions based on individual cognitive profiles. © 2025 Elsevier Ltd