A 35-year-old female patient was scheduled for a left hemithyroidectomy. We performed bilateral cervical plexus blocks with ultrasound guidance for an awake thyroidectomy. Soon after the blocks, she developed a weak voice, which gradually progressed to complete aphonia. Due to her apprehension, general anesthesia was administered. After an uneventful surgery, the patient spontaneously regained her normal voice in the postoperative period. The case report describes a previously unreported complication of aphonia presumably due to bilateral recurrent laryngeal nerve blocks, which might have occurred from the infiltrated local anesthetic extravasating to the deeper planes through the cervical fascia.