Objective: To summarize the clinical features, management and outcome of superior vena cava syndrome (SVCS) associated with mediastinal malignancy in children. Methods: Clinical data of 42 children of SVSC associated with mediastinal malignancy in Shanghai Children's Medical Center from January 2015 to December 2021 were collected and analyzed retrospectively. The clinical manifestations, pathological diagnosis, disease diagnosis process, and prognosis were summarized. Results: Among 42 children of SVCS associated with mediastinal malignancy, there were 31 males and 11 females. The age at diagnosis was 8.5 (1.9, 14.9) years. Cough and wheezing (33 cases, 79%), orthopnea (19 cases, 45%) and facial edema (18 cases, 43%) occurred most commonly. T-cell lymphoblastic lymphoma (T-LBL) was the most frequent pathological diagnosis (25 cases, 60%), followed by T-cell acute lymphoblastic leukemia (T-ALL) (7 cases, 17%), anaplastic large cell lymphoma (4 cases, 10%) and diffuse large B-cell lymphoma (2 cases, 5%), peripheral T-lymphoma, Hodgkin lymphoma, Ewing's sarcoma and germ cell tumor (1 case each). Pathological diagnosis was confirmed by bone marrow aspiration or thoracentesis in 14 cases, peripheral lymph node biopsy in 6 cases, and mediastinal biopsy in 22 cases. Twenty-seven cases (64%) had local anesthesia. Respiratory complications due to mediastinal mass developed in 3 of 15 cases who received general anesthesia. Of the 42 cases, 27 cases had sustained remission, 1 case survived with second-line therapy after recurrence, and 14 cases died (2 cases died of perioperative complications and 12 cases died of recurrence or progression of primary disease). The follow-up time was 36.7 (1.2, 76.1) months for 27 cases in continuous complete remission. The 3-year overall survival (OS) and events free survival (EFS) rates of 42 children were 59% (95%CI 44%-79%) and 58% (95%CI 44%-77%) respectively. Conclusions: SVCS associated with mediastinal malignancy in children is a life-threatening tumor emergency with high mortality. The most common primary disease is T-LBL. The most common clinical symptoms and signs are cough, wheezing, orthopnea and facial edema. Clinical management should be based on the premise of stable critical condition and confirm the pathological diagnosis through minimal invasive operation.