Background <p>Undifferentiated pleomorphic sarcoma arising from the posterior mediastinum and infiltrating the thoracic aorta is exceptionally rare, with few cases reported in scientific literature.</p> Case presentation <p>A 48-year-old Han Chinese man was admitted with persistent chest pain for 2 months; he had not received a diagnosis or treatment plan from the previous hospital. Firstly, thoracic endovascular aortic repair surgery was performed to safeguard the integrity of the thoracic aorta, followed by a biopsy to confirm undifferentiated pleomorphic sarcoma. A chemotherapy plan was then established on the basis of the latest pathological results.</p> Conclusion <p>Undifferentiated pleomorphic sarcoma is highly malignant, complicating diagnosis and treatment and often resulting in a poor prognosis. Invasion of the posterior mediastinum and aorta is exceptionally rare. An early thoracic endovascular aortic repair intervention to protect the aorta and cut tumor blood supply, followed by needle biopsy for diagnosis, offers an innovative approach that can guide clinical practice.</p> Graphical abstract <p></p>