Introduction: Mediastinal parathyroid adenoma localization is a rare entity. We report a case of excision by manubriotomy of intrathymic parathyroid adenoma detected by Computed Tomography scan of the chest and neck and confirmed by Technetium-99 m-sestamibi scan (99 mTc-MIBI). Case Presentation: A 68 years old woman with history of hypercalcaemia, PTH elevation and operation for pathological fracture of the left femur 7 days before was presented to our service. The patient underwent manubriotomy and the adenoma was found within the right lobe of the thymus gland. Conclusion: The Technetium-99 m-sestamibi scan evaluation can be useful in the preoperative localization of ectopic parathyroid adenomas. The surgical approach by manubriotomy is privileged when the ectopic adenoma is in the upper part of anterior mediastinum.