Cervico-thoracic paragangliomas are rare hypervascular neuroendocrine tumors, with high morbidity and mortality due to locally invasive growth. They are often misdiagnosed in patients with cervical masses. Horner's syndrome, in this case, results from a lesion of the stellate ganglion. Only a few cases in the literature describe paragangliomas affecting the stellate ganglion [1,2]. We report the case of a 61-year-old female with a cervico-thoracic paraganglioma associated with Horner's syndrome. She had no significant medical history. Cervical computed tomography (CT) and magnetic resonance imaging (MRI) revealed a large, highly vascularized antero-superior mediastinal mass measuring 6.8 cm x 5 cm x 9 cm, surrounding the left subclavian and carotid arteries, and slightly compressing the trachea, esophagus, and innominate vein. Surgery provided the definitive diagnosis through histopathological analysis. We highlight the different types of paragangliomas and the challenges in diagnosis. A 2-year follow-up with CT and PET-CT scans confirmed no recurrence of the lesion. Paragangliomas are rare, slow-growing neuroendocrine tumors that may appear wherever autonomic ganglia are present. Clinical presentations vary, including lesions of the stellate ganglion causing ipsilateral Horner's syndrome. Paragangliomas should be considered in the differential diagnosis of cervico-thoracic masses. Treatment involves complete surgical resection while preserving neurovascular structures [3].