Fahr's syndrome is a rare neurodegenerative condition characterized by bilateral progressive calcification of the basal ganglia and other brain structures. Due to overlapping symptoms, it can be misdiagnosed as other neurological disorders. Case presentation: A 68-year-old man was presented to the emergency department with an exacerbating decline in the level of consciousness and dysarthria over a 20-day period. On admission, the laboratory examinations revealed a low level of calcium and parathyroid hormone. Brain imaging findings showed bilateral calcifications in the basal ganglia, pulvinar region of the thalami, and dentate nuclei. In addition, a prolonged QTc interval on his electrocardiogram (ECG) indicated hypocalcemia. After receiving calcium gluconate 10%, the calcium level and QTc interval stabilized, and the patient's level of consciousness gradually improved. Conclusion: Fahr's syndrome due to hypoparathyroidism should be suspected in any patient with neurological symptoms and hypocalcemia. Hence, early identification and management of hypoparathyroidism can prevent progression of calcification and improve patients' quality of life and prognosis.