Background: The overall prevalence of borderline personality disorder is well known, but characteristics of offender patients with the condition are less clear, especially among men. Aim: Describe characteristics of men and women with borderline personality disorder in special psychiatric units in Dutch prisons on three domains: prevalence of child abuse, comorbidity of borderline personality disorder with other disorders, and clinical symptoms. Methods: One hundred and sixty-seven people were assigned to this study based on a Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5) diagnoses retrieved from records. Other DSM-5 diagnoses were also recorded. Two scales, the Dutch Historisch, Klinisch, Toekomst—Revisie and the international Brief Psychiatric Rating Scale—Expanded (BPRS-E) were used to record child abuse and clinical symptoms, respectively. Results: Prevalence rates of child abuse were high, but the men and women did not differ in this respect. The male offender patients were more likely than the women to have a comorbid substance use disorder, whereas the women were more likely to have a comorbid anxiety disorder. Intellectual disability was the most common comorbid Axis II disorder. The women were more likely than the men to have committed a fatal/nearly fatal index offence and showed higher rates of distress or behavioural disturbance on all five BPRS-E factors. Conclusions: This study provides evidence of the importance of in-depth knowledge of presentations with borderline personality disorder specific to setting. Although we were unable to make direct comparisons with other samples, our figures suggest clinically relevant differences among offender patients from the more widely reported general samples. We also shed light on a sometimes underexposed group of men with borderline personality disorder and their clinical needs. More population-specific intervention and follow-up studies are now indicated.