Vocal cord paralysis associated with goiter usually indicates the presence of a malignancy. Pediatric patients retain significant thymic tissue that regresses only later in life. This thymic tissue can develop significant hyperplasia during an acute autoimmune process. We describe a case of a 17-year-old girl who presented with a goiter secondary to severe Graves’ disease and a 2-month history of hoarseness, choking on liquid intake, and small-volume vomiting especially after eating. She demonstrated a left vocal cord paralysis probably secondary to a unilateral left recurrent laryngeal nerve palsy. A marked enlargement of the thymus was discovered on thoracic imaging. Treatment was initiated with methimazole, with near complete remission of her vocal cord paralysis within 3 months. Given the immunomodulatory effects of methimazole, a potential mechanism of the left recurrent laryngeal nerve palsy was autoimmune hyperstimulation of the thymus and consequent hyperplasia, resulting in distension of the nerve. Attenuation of the hyperactive immune process with methimazole may have resulted in regression of the mass effect of the thymus and associated reduction of the nerve distension. This case illustrates the unique risk of left recurrent laryngeal nerve palsy in pediatric patients with an acute immune stimulation and hyperplasia of the thymus and the reversibility in the context of mitigation of the immune hyperactivity. Methimazole may be an optimal initial treatment choice in pediatric patients with Graves’ disease and left recurrent laryngeal nerve palsy.