Hyperparathyroidism and concurrent thyroid nodular disease are prominent. In contrast, concomitant papillary thyroid cancer and hyperparathyroidism are uncommon (1%–2%). Parathyroid adenomas in unusual locations are difficult to detect by conventional diagnostic imaging. 99mTc-sestamibi single-photon emission computed tomography/computed tomography (SPECT/CT) has increased the localizing success rate of these lesions since it provides specific functional and anatomical information, improving exploratory parathyroid surgery planning and decreasing operative time, unnecessary dissections, complications, and morbidity. We confirmed its usefulness in a patient with an occult parathyroid adenoma that was clearly identified by 99mTc-sestamibi SPECT/CT 2 weeks after a thyroidectomy for papillary carcinoma. The SPECT/CT results allowed us to successfully perform efficient reexploration of the thyroid bed, in a retroesophageal parathyroid adenoma by minimally invasive surgery.