Schwannomas are rare, benign, slowly growing neurogenic tumors that originate in peripheral, spinal, or cranial nerves other than the optic and olfactory nerves. In the head and neck, these tumors usually arise from the vagus nerve and the cervical sympathetic chain in the parapharyngeal space. Cervical sympathetic chain schwannomas represent a rare subgroup of schwannomas; fewer than 60 cases have been reported in the literature. These tumors are rarely seen in children and adolescents. Because patients typically present with an asymptomatic neck mass and vague complaints, clinical suspicion is important in making the diagnosis. Neural deficits at presentation are uncommon. The presence of features of Horner syndrome before excision is very rare, having been previously reported in only 10 cases of cervical sympathetic chain schwannoma. We report an extremely rare case of a cervical sympathetic chain schwannoma in a child who presented with Horner syndrome. The lesion was successfully excised.