A 52-year-old woman presented with a complaint of neck swelling. The patient showed signs of hyperparathyroidism: hypercalcemia, and hypophosphatemia. Tc-99m MIBI dual-phase parathyroid scintigraphy and SPECT revealed increased activity in a regular-bordered, “doughnut”-shaped mass on the left side of the thyroid gland with a central hypoactive area. The cervical ultrasound identified a mixed echoic thyroid nodule with a central large cystic portion, and no parathyroid gland abnormality. Total thyroidectomy and parathyroid exploration was performed. Pathological evaluation of the resected thyroid specimen reported a giant intra-thyroidal hemorrhagic parathyroid adenoma.