Ectopic parathyroid adenomas (PAs) can occur in numerous locations and are thought to be the cause of a significant portion of failed primary surgery for hyperparathyroidism. PA is a rare cause of hoarseness, which may be harbingers of a malignant process. Here, we describe an unusual case of an ectopic PA in the carotid sheath presenting as unilateral vocal cord paralysis (VCP). A 49-year-old lady presented with a 1-week history of hoarseness, irritating cough and shortness of breath. Fibreoptic laryngoscopy revealed left VCP. Ultrasound and computed tomography of the neck demonstrated a mass in the carotid sheath. Laboratory investigations revealed hypercalcemia (3.10 mmol/L), hypophosphatemia (0.81 mmol/L) and elevated intact parathyroid hormone (iPTH) level (381.6 pg/mL), despite of a negative 99mTc-sestamibi scan. After more rigorous tests, the ectopic tumor adjacent to the left vagus nerve was successfully resected, with subsequent histopathological confirmation of PA. The patient eventually got a normal iPTH level and serum calcium postoperatively, and regular voice function was also regained 4 months after surgery. This case emphasizes the importance of broad differential diagnosis and thorough workup. Although most patients with PA present with hypercalcemia, this disease entity also need to be considered in the differentials of neck masses and VCP.