Intra-operative parathyroid hormone (IOPTH) assay is a useful tool to confirm complete excision of all hyper-functioning parathyroid gland tissue. In this report, we describe a case with successful localization of distant metastasis in a patient with parathyroid carcinoma using the IOPTH assay. A 53-year-old man presented to our clinic with a serum calcium level of 11.8 mg/dL and an intact PTH level of 233.3 pg/mL. He had been treated for parathyroid carcinoma eleven years ago. Two suspected metastatic lesions were detected on the chest computed tomography. Due to the vastly different surgical field necessary to excise each lesion, we preferentially removed only one lesion and we monitored the other remaining suspected lesion without resection via IOPTH assay. Six months later, the patient's serum calcium and intact PTH levels remained within their normal ranges. To the best of our knowledge, this is the first case to effectively utilize IOPTH assay for the management of metastatic parathyroid carcinoma.