Background: Several studies have suggested that immigrants have higher rates of psychiatric emergency service use and a higher risk of mental disorders such as schizophrenia than indigenous populations. Aims: To compare the likelihood that immigrants (immigrant group) v. indigenous population (indigenous group) will be diagnosed with borderline personality disorder in a psychiatric emergency service and to determine differences according to area of origin. Method: A total of 11 578 consecutive admissions over a 4-year period at a tertiary psychiatric emergency service were reviewed. The collected data included socio-demographic and clinical variables and the Severity of Psychiatric Illness rating score. Psychiatric diagnosis was limited to information available in the emergency room given that a structured interview is not usually feasible in this setting. The diagnosis of borderline personality disorder was based on DSM-IV criteria. Immigrants were divided into five groups according to region of origin: North Africa, sub-Saharan Africa, South America, Asia and Western countries. Results: Multivariate statistical logistic regression analysis showed that all subgroups of immigrants had a lower likelihood of being diagnosed with borderline personality disorder than the indigenous population independently of age and gender. Furthermore, the rates of borderline personality disorder diagnosis were considerably lower in Asian and sub-Saharan subgroups than in South American, North African, Western or native subgroups. Conclusions: Our results showed that in the psychiatric emergency service borderline personality disorder was diagnosed less frequently in the immigrant group v. the indigenous group. Our results do not support the concept of migration as a risk factor for borderline personality disorder.