Background: Autoimmune diseases and schizophrenia share many common features. Association studies confirm a shared genetic association in the human leukocyte antigen (HLA) region between schizophrenia and most autoimmune diseases. To our knowledge, the simultaneous syndromes of Graves’ disease (GD) and type 2 diabetes (T2D) in schizophrenia are rare in Tunisia.Case presentation: We report a case of a 42-year-old woman admitted to the department of psychiatry for an acute relapse of chronic schizophreniHer medical history revealed that she was followed for Graves’ disease and for a type 2 diabetes mellitus. A low-resolution HLA typing was performed by polymerase chain reaction sequence-specific primer (PCR-SSP) techniques according to determine the patient’s haplotype. Conclusions: Our study suggests that the HLA DRB103 allele may explain a common etiology underlying the co-morbidity of Graves’ disease, type 2 diabetes, and schizophrenia in our patient.