Patients commonly complain of discomfort at the angle of the mouth following tonsillectomy. This can be attributed to trauma sustained during the procedure. A prospective, patient-blinded, controlled trial of 34 tonsillectomies was performed using a protective, plastic oral guard. A blinded observer recorded postoperative pain and clinically evident trauma to the angle of the mouth. The patient group in whom the guard was used had a significantly lower incidence of labial trauma (p<0.002) and complained of pain less frequently (p<0.002) when compared with a control group in whom no guard was used. The use of a protective lip guard during tonsillectomy is recommended.