Intermittent Explosive Disorder (IED) is characterized by impulsive aggression, often with heightened hostile attributions of ambiguous social situations. This study examined whether individuals with IED exhibit idiosyncratic neural responses to ambiguous social cues, using intersubject correlation (ISC) analyses during a naturalistic video-based task. Forty-five adults (19 with IED) viewed videos depicting social interactions with adverse endings with ambiguous intentions or control neutral endings while undergoing fMRI scanning. Compared to healthy participants, IED individuals demonstrated heightened hostile attributions and stronger negative emotional responses. Crucially, a linear mixed effect model of ISCs revealed reduced neural synchrony in dyads including IED participants, particularly in regions implicated in social cognition and self-referential processing, such as the precuneus, insula, superior temporal sulcus, intraparietal sulcus, orbitofrontal cortex, and dorsomedial prefrontal cortex. These findings suggest that individuals with IED interpret ambiguous social situations in a more idiosyncratic manner, contributing to maladaptive social perceptions and aggression. The use of ecologically valid stimuli provides novel insights into the neural mechanisms underlying hostile attribution in IED, offering potential targets for interventions aimed at promoting adaptive social cognition and reducing impulsive aggression.