During transoral endoscopic thyroidectomy vestibular approach (TOETVA), the mental nerve can be injured by the lateral ports. Mental nerve injury is a worrisome complication, which can be minimized by using the single-port platform. A 56-year-old woman was diagnosed with a 5-mm sized papillary thyroid carcinoma on the isthmus. A horizontal 21-mm incision was made on the mucosa at the lower lip, followed by vertical dissection from the mentalis muscles down to the mandibular area. Subsequent hydrodissection widened the working space. For the single-port procedure, the KeyPort system was applied. After inserting the endoscopic instruments, the thyroid isthmus was resected as usual. The patient was discharged without any complications. To our knowledge, this is the first report of single-port TOETVA. Although the indications are limited, a single-port platform can be utilized for TOETVA. This will minimize the risk of mental nerve injury.