The purpose of the present investigation was to explore and better understand the relationship between justice sensitivity from a victim's perspective (JS-victim) and interpersonal forgiveness. In particular, we aimed to identify the cognitive mechanisms mediating this relationship and test the moderating influence of post-transgression perpetrator behavior. We used data from a questionnaire study employing a Swiss community sample (N = 450) and 2 scenario-based studies employing German online samples, in the context of romantic (N = 242) and friendship relationships (N = 974). We consistently found JS-victim to be negatively related to dispositional (Study 1) and situational forgiveness (Studies 2 and 3). Study 2 demonstrated the relationship between JS-victim and reduced forgiveness to be partly mediated by mistrustful interpretations of the partner's post-transgression behavior. In Study 3, cognitions legitimizing one's own antisocial reactions and a lack of pro-relationship cognitions were identified as further mediators. These variables mediated the negative effect of JS-victim on forgiveness largely independent of whether the friend perpetrator displayed reconciliatory behavior or not. Findings suggest that the cognitive mechanisms mediating victim-sensitive individuals' unforgiveness could barely be neutralized. Future research should investigate their malleability in light of qualitatively different perpetrator behaviors as well as their broader relational implications.