Background: Mediastinal hemangiomas are extremely rare benign vascular neoplasms, accounting for less than 0.5% of all diagnosed mediastinal masses. Primary origin from or direct involvement of the walls of the right superior vena cava (SVC) is exceptionally uncommon. We present the case of a 31-year-old man with a 6-month history of recurrent upper respiratory tract infections. Chest radiography showed displacement of the tracheal midline, and noncontrast computed tomography demonstrated a large anterior mediastinal tumor arising from the right SVC. Complete surgical excision was performed through an open transthoracic approach to ensure safe vascular control. Intraoperative findings included abundant thymic fat, multiple dense fibrous adhesions, and a 5 × 6 cm tumor involving the superior jugular vein, right pleura, and pericardium, as well as periaortic neovascularization. Definitive histopathologic examination confirmed a cavernous hemangioma with dystrophic calcification arising in residual thymic and adipose tissue and showed positive surgical margins (R1 resection) in the specimens from the mediastinal tumor, the SVC extension, and the periaortic tissue. Because of the absence of a true fibrous capsule and the lesion’s intimate fusion with the adventitia of the great vessels, achieving microscopically negative margins (R0) is highly challenging when preservation of vascular structural integrity is prioritized. Therefore, after an R1 resection, although the benign nature of the lesion precludes metastatic potential, strict long-term clinical and imaging surveillance with serial CT scans is required to monitor for possible local recurrence. Keywords: Cavernous hemangioma, Anterior mediastinum, Superior vena cava, Surgical margins, Vascular control.