ABSTRACT Maladaptive schemas have been linked with increased posttraumatic stress disorder (PTSD) symptoms. Posttraumatic negative self-appraisals (i.e., posttraumatic shame and self-blame) have also been empirically supported as contributors to PTSD symptom severity following traumatic events. These associations are well known; however, the pathways between maladaptive schemas and PTSD symptoms remain largely unclear. The present study aimed to examine the mediating effects of posttraumatic negative self-appraisals (shame and self-blame) on the association between maladaptive schemas and PTSD symptom severity in patients completing a partial hospitalization program. Patients (N = 98) completed measures of early maladaptive schemas, posttraumatic shame, posttraumatic self-blame, and PTSD symptom severity at intake. Posttraumatic negative self-appraisals mediated the association between maladaptive schemas and PTSD symptom severity. When we examined the specific mediating effects of shame and blame – rather than negative self-appraisals overall – shame was a significant mediator (b = .153, 95% CI [.031, .296]), but not blame (b = .038, 95% CI [−.083, .204]). Further, posttraumatic shame mediated the association between two of the four schema domains – disconnection & rejection (b = .092, 95% CI [.030, .201]) and impaired autonomy & performance (b = .047, 95% CI [.002, .124]) – and PTSD symptom severity. These findings highlight the importance of posttraumatic shame in the association between maladaptive schemas and PTSD symptom severity. Theoretical and practical implications are discussed.