Introduction Insulinomas constituting the most common cause of endogenous hyperinsulinism-related hypoglycemia are neuroendocrine tumors originating from pancreatic beta cells. They are generally benign and solitary lesions. Although most cases are sporadic, multiple endocrine neoplasia (MEN) 1-related patients are also present. Material and Method Thirteen patients followed up in Bursa Uludağ University Medical Faculty Endocrinology and Metabolic diseases clinic between the years 2012 and 2021 were retrospectively evaluated. Demographical, clinical, biochemical, radiological and histopathological data of the patients were assessed. Results Eight of the patients were females, and five were males with an average age of 43±14.9 years. Ten of the patients had sporadic, and three had MEN1 syndrome-related insulinoma. During the prolonged fasting test, the patients had a mean lowest plasma glucose level of 36.4 ± 6.2 mg/dl with a simultaneous mean insulin level of 11.3 (4.4 - 214.1) mIU/L and c-peptide level of 2.8 (0.46-12.8) mcg/L. In preoperative localization studies, a lesion was detected in 11 out of 13 (84.6%) patients with upper abdominal computed tomography (CT) and 6 out of 10 patients (60%) with magnetic resonance imaging (MRI). Six patients had grade 1, and 7 patients had grade 2 neuroendocrine tumor. The whole group's mean lesion diameter was 15 (11-48) mm. The mean patient follow-up duration was 30.5 ± 23 months. Hypoglycemia recurred in none of the patients in the postoperative period, and only two patients (15.4%) developed postoperative diabetes mellitus (DM). Conclusion Preoperative localization rates in insulinomas increased due to non-invasive imaging methods and technological developments in recent years. This will probably cause earlier diagnosis and treatment, and pancreas preserving surgery option will be more available in most insulinoma cases.