Primary hyperparathyroidism (PHPT) is a prevalent endocrine condition that presents with significant clinical symptoms. Ectopic adenomas commonly occur in the tracheo-esophageal groove, thymus, intrathyroidal, and mediastinum. While mediastinal ectopic adenomas are frequently observed, pericardial ectopic adenomas are only documented in case reports in the literature.We present a 65-year-old female patient who had persistent PHPT and underwent re-sternotomy and excision of a pericardial ectopic parathyroid adenoma. The typical treatment for PHPT has generally been conventional bilateral neck exploration without preoperative imaging. Conventional bilateral neck exploration has decreased in popularity because of the rise in the minimally invasive parathyroidectomy (MIP) procedure. The use of MIP is prevalent in surgical procedures, and it is crucial to have precise preoperative localization. Due to the ectopic localization of certain parathyroid adenomas, they are regarded as an important cause of the failure of primary surgery. Hence, particularly when dealing with persistent and recurrent PHPT, modern imaging techniques like 4D CT enhance the efficacy of surgical interventions. Therefore, particularly in cases of ectopic parathyroid adenomas located in the mediastinum, it is important to consider the possibility that if the adenoma cannot be found after surgery, it may be located in the pericardial region.