Type 1 diabetes mellitus may be associated with many autoimmune diseases with the common autoimmune pathogenesis. We describe the case of a girl suffering from Type 1 diabetes mellitus and autoimmune Hashimoto's thyroiditis since the childhood and, due to the onset of Juvenile Idiopathic Arthritis during adolescence, for three years practiced therapy with an anti-TNF drug, etanercept . Currently her inflammatory markers are normal, arthritis is inactive and diabetes is well controlled. During the treatment with anti-TNF drug we observed a significative reduction of insulin dose, probably due to an increased tissue sensitivity secondary to the suppression of the activity of TNF-alpha. Several clinical trials that have evaluated the effect of immunomodulatory agents in diabetic patients, especially in those with recent onset of disease, were already performed but further studies of longer duration on a larger population are needed to assess the role of biologic drugs and immunotherapy in this group of patients.