Among all hormone-secreting pancreatic tumors in dogs, insulinoma occurs most commonly. Insulinoma is capable of secreting substances that reduce the blood glucose level - mainly insulin, sometimes insulin growth factor type 1 (IGF-1) - which results in chronic hypoglycemia. Since the organism usually adapts to a depressed blood glucose level, insulinoma manifests itself clinically when demand for glucose is highly elevated, e.g., during physical exertion. Seizures resulting from impaired central nervous system function are the most common clinical manifestation. A ten-year-old female Amstaff was presented to the Clinic of Small Animals because of seizures, which had been periodically observed for the previous two weeks. Laboratory and imaging diagnostic procedures enabled a tentative diagnosis of insulinoma, which was subsequently confirmed by exploratory surgery. The main objective of the case description was to remind veterinarians about insulinoma, a metabolic cause of seizures. It is worth noting that a normal blood glucose level after an episode of seizures does not rule out insulinoma as a cause of this clinical condition.