Background and Aims: Gender identity disorder (GID) is characterized by a strong and persistent identification with the other gender, followed by a continuous discomfort and dissatisfaction with current gender that can affect social, occupational and other aspects of functioning. Previous studies report high prevalence of comorbid personality disorders with GID, especially narcissistic and borderline personality disorders (BPD). Our aim was to discuss the diagnosis of GID in a patient with BPD and narcissistic traits. Methods: We present a case report with detailed medical history and diagnostic work-up. Results: A 19-year-old female patient was admitted to a psychiatric clinic in Croatia due to psychotic decompensation with intense depersonalization phenomena, imperative auditory hallucinations, suicidality and frequent self-mutilating behavior. In a couple of days, she revealed her cross-gender identification accompanied by feelings of repulsion and discomfort towards her body and started to present as a male with a new, male name. During the treatment, characteristics of BPD with narcissistic elements and impulsive behavior came in the first plan, with frequent changes of therapists and psychiatric clinics later-on. Identification with male gender persisted despite the thoughts that she could never become a perfect man which was her goal concordant with the narcissistic traits of her personality. Conclusions: The case of our patient questions the line between identity disorder as a part of BPD and specific disorder in gender and sexual identity. Is it a symptom of BPD, or GID with comorbid BPD diagnosis?