Primary hyperparathyroidism (pHPT) is typically caused by a parathyroid adenoma, although some cases arise from ectopic glands. Accurate preoperative localization is essential for guiding surgical strategy, particularly for mediastinal lesions. We report successful video-assisted thoracoscopic surgery (VATS) for an upper mediastinal parathyroid adenoma. A 68-year-old woman was referred for hypercalcemia during evaluation for recurrent ureteral stones. Laboratory tests revealed elevated serum calcium (13.2 mg/dl) and intact parathyroid hormone (iPTH) levels (266 pg/ml). Contrast-enhanced computed tomography, magnetic resonance imaging, and 99mTc-methoxyisobutylisonitrile scintigraphy identified a 20-mm mass adjacent to the right esophageal wall. VATS was performed due to the tumor’s mediastinal location. The lesion was resected with intraoperative nerve monitoring (IONM) to avoid recurrent laryngeal nerve damage. Postoperatively, iPTH and calcium levels rapidly normalized. Transient hypocalcemia and mild hoarseness occurred but resolved with calcium supplementation and conservative management. Pathological examination confirmed a parathyroid adenoma without malignancy. VATS offers a safe and minimally invasive approach for upper mediastinal parathyroid adenomas. IONM and vigilant calcium management are crucial for minimizing these complications. This case highlights the importance of comprehensive imaging, surgical planning, and postoperative care in managing upper mediastinal pHPT.