Research indicates that intensive trauma-focused therapy can be effective in alleviating symptoms of post-traumatic stress disorder (PTSD) and borderline personality disorder (BPD). However, these studies have relied on self-report of BPD symptoms and follow-up data are scarce. The purpose of this feasibility study was to determine the effects of an intensive trauma-focused treatment programme on the severity of PTSD and BPD symptoms and the diagnostic status up to a 12-month follow-up. A total of 45 (60% female) individuals meeting the diagnostic criteria of both PTSD and BPD participated in an intensive eight-day trauma-focused treatment programme which combined prolonged exposure and EMDR therapy in an inpatient treatment setting. Severity of PTSD and BPD symptoms were assessed at pre-treatment, post-treatment, 6 months, and 12 months after treatment (CAPS-5, BPDSI-IV). Diagnostic status was determined using clinical interviews (CAPS-5 and SCID-5-P) at pre-treatment and 12-month follow-up. Of all participants, 93.3% had been exposed to physical abuse, and 71.1% to sexual abuse prior to the age of 12 years. PTSD and BPD symptom severity significantly decreased from pre- to post-treatment (Cohen's : 1.58 and 0.98, respectively), and these results were maintained at 6- (: 1.20 and 1.01) and 12-month follow-up (: 1.53 and 1.36). Based upon CAPS-5, 69.2% no longer met the diagnostic criteria of PTSD at 12-month follow-up, while according to the SCID-5-P 73.1% no longer fulfilled the diagnostic criteria of BPD at that time. No significant worsening of symptoms occurred. The findings of this study, which is the first to examine the effects of psychotherapeutic treatment of PTSD on the presence of a borderline personality disorder one year after treatment, add support to the notion that a brief intensive trauma-focused treatment can be a valuable option for individuals suffering from both PTSD and BPD.