BackgroundSchwannomas are benign, well-differentiated tumors that originate from Schwann cells. Involvement of the cervical sympathetic nerve is relatively rare. Computed tomography is indispensable for the diagnosis. The treatment is surgical. Histological examination confirms the diagnosis. Horner’s syndrome postoperatively is supportive of the diagnosis. The rarity of giant cervical sympathetic chain schwannoma made the case of our patient interesting to report. Furthermore, our patient’s immense tumor size is very rare, and we could not find any similar report in the literature. Cervical sympathetic chain schwannoma is frequently confused with schwannoma of the vagus nerve on clinical and radiological examination, and its diagnosis can therefore be challenging for clinicians, radiologists, and pathologists.Case presentationWe report a rare case of cervical schwannoma in a 40-year-old Moroccan woman who presented with a large parapharyngeal mass. Computed tomography revealed a giant, heterogeneous, well-defined mass measuring 110 × 100 × 147 mm, occupying the right carotid triangle, and descending to the superior mediastinum. Surgical excision with a transcervical approach was done. Histological examination confirmed the diagnosis. The patient’s postoperative course was marked by Horner’s syndrome.ConclusionsCervical sympathetic chain schwannoma is a rare, benign tumor. It should be considered in the differential diagnosis in patients presenting with a lateral neck mass. Surgical exploration must be discussed for a tumor with a large volume.