Insulinomas are usually functional, neuroendocrine tumor of the β cells of the pancreas. With an incidence of 22% compared to other reported tumors in ferrets, they are the most commonly reported. Chronic hypoglycemia is characteristic for the disease, as well as clinical symptoms such as ataxia of the hind limbs, lethargy, and collapse. The severity of clinical symptoms increases as the disease progresses, finally emerging as irreversible cerebral lesions. Diagnostics are based on a combination of characteristic clinical symptoms and a low concentration of glucose in the blood, whilst a final diagnosis is made only after a pathohistological analysis. Insulinoma is a disease that cannot be cured but can be treated. Therapy is medical or surgical or a combination of both. This study included 50 ferrets that were admitted to the Clinic for Internal Diseases at the Faculty of Veterinary Medicine, in Zagreb, in an 8 year period which were then diagnosed with insulinomas. A mild sexual predisposition (in favor of males) was noticed and the disease is found to be more common in middle-aged ferrets. The most common symptoms observed were ataxia of the hind limbs, lethargy, collapse, a loss of weight and a loss of appetite. Based on diagnostic data, we have confirmed the most common diagnostic procedure is measuring the concentration of glucose in the blood, as well as that medical therapy is the most commonly chosen method of therapy.