Recurrent hyperparathyroidism (HPT) after initial parathyroid surgery occurs rarely in an ectopic location. The rare phenomenon of parathyromatosis may be the cause of this. We present the case of a 59-year-old woman with recurrent HPT, which presented as a new ectopic mediastinal parathyroid gland 13 years after initial 3.5 gland parathyroidectomy. A 1.5 × 1.3 cm lesion was discovered as an incidental finding in the pretracheal region, closely abutting the aortic arch. An aspirate revealed oncocytic cells, which were positive for parathyroid hormone, confirming a mediastinal parathyroid nodule. Sestamibi scan confirmed an avid nodule in the mediastinum. This patient had multiple co-morbidities but was asymptomatic of HPT. It was therefore decided at multi-disciplinary team discussion that she should undergo surveillance. To our knowledge, no such presentations have been reported in the literature. Thus, our case report is a unique addition of an atypical presentation of HPT. [ABSTRACT FROM AUTHOR]