Background: Posttraumatic stress disorder (PTSD) is common in patients with personality disorders. This comorbidity is accompanied by a lower quality of life, and a higher risk of suicide attempts than patients with only one of these diagnoses. Objective: The aim of this systematic review and meta-analysis was to evaluate the scientific evidence of the efficacy of PTSD treatments for this population. Method: A literature search was performed from 1946 through June 2020. Standardized mean effect sizes of psychotherapy for PTSD were computed. Results: The literature search revealed that psychotherapy was the only intervention that was systematically explored. Fourteen studies were included. In 12 of these studies solely patients with borderline personality disorder participated. Analysis of the four RCTs showed a significant, moderate to high standardized effect size for reducing PTSD symptom severity (Hedges' g = 0.54), with effects being maintained at least 3 months (Hedges' g = 0.82). Effect sizes for all studies were also significant, with moderate to high standardized values for symptoms of PTSD (Hedges' g = 1.04). PTSD improvements were again maintained at 3-month follow-up and beyond (Hedges' g = 0.98). In addition, a significant decrease in symptoms of depression, anxiety, borderline symptoms, and PTSD in patients with borderline personality disorder could be revealed for all studies (Hedges' g 0.48-1.04). No increase in self-injurious behaviour, suicide attempts, or hospitalization was observed, while the mean weighted dropout rate during PTSD treatment was 17%. Conclusions: Psychotherapy for PTSD is efficacious and safe for patients with borderline personality disorder and should not be withheld from these vulnerable individuals. Keywords: borderline personality disorder; clinical trial; efficacy; psychotherapy; safety; trauma; • Psychotherapy reduces PTSD symptom severity in patients with borderline personality disorder.• The duration of the reduction of PTSD symptom severity after psychotherapy is at least three months.• Risks associated with psychotherapy for PTSD are low in this population..