Introduction: Personality disorders are a group of behavioural patterns associated with significant personal and socio-occupational disturbances. Numerous studies have demonstrated borderline personality to be one of the most common personality disorders. It’s less often diagnosed with just a clinical assessment. Aim: To examine the proportion of patients with Borderline Personality Disorder (BPD), and its associated personality types and clinical syndromes, using the Millon Clinical Multiaxial Inventory version-III (MCMI-III). Materials and Methods: A retrospective observational study was carried out on 450 adult patients who attended the psychiatry outpatient department of an urban tertiary care hospital. They had been administered the MCMI-III, a self-rating questionnaire commonly used to provide information on personality types and associated clinical syndromes. Statistical Package for the Social Sciences (IBM SPSS, Windows) version 20.0 was used for statistical analyses. Data was expressed in terms of actual number, mean and percentages. Chi-Square or Fisher’s-exact test, as appropriate, was used for categorical data to test for associations. Odds ratio was estimated to measure strength of the association. Results: Borderline was the most common personality type comprising nearly half (46.63%) of the study population. 25.5% had borderline traits while 21.1% had Borderline Personality Disorder (BPD). BPD was significantly higher in females (p<0.001), younger age group below the age of 40 years (p<0.001) and unmarried persons (p<0.001). It was comorbid most with Anxiety (90.91%; OR=4.05; p<0.001), Major Depression (85.23%; OR=18.39; p<0.001), Post Traumatic Stress Disorder (PTSD) (46.59%; OR=6.30; p<0.001) and Thought disorders (56.82%; OR=18.15; p<0.001). Alcohol (22.73%; OR=3.54; p<0.001) and Drug dependence (13.64%; OR=11.52; p<0.001) were also seen significantly higher in patients with BPD. Personality types significantly comorbid with BPD were Sadistic, Depressive, Masochistic, Negativistic, Schizotypal, Avoidant, Dependent, Antisocial and Paranoid types, with odds being most for Sadistic personality (OR=9.44). Conclusion: It is recommended that mental health professionals and clinicians should start to look for underlying symptoms of BPD in patients of anxiety and mood syndromes. If found these patients should be directed for psychotherapy as early as possible. The MCMI psychological test would be an important contribution to this area, given the need for systematic, quick, and objective testing methods that facilitate the diagnosis.