Abstract: Objective To evaluate the impact of postoperative adjuvant radiotherapy on the survival benefits of patients with complete resection of type B2 thymoma, providing evidence for postoperative adjuvant radiotherapy. Methods A total of 154 patients with type B2 thymoma who were treated from September 2008 to January 2024 at the Affiliated Hospital of Xuzhou Medical University, Xuzhou Central Hospital, and Xuzhou Cancer Hospital were selected. Based on treatment modality, the patients were divided into two groups: a surgery group (n=72) and a surgery + radiotherapy group (n=82). Their general data, clinical characteristics, and radiotherapy-related data were collected. Kaplan-Meier survival analysis was conducted. Cox univariate and multivariate regression models were used to analyze the risk factors affecting patient prognosis. Results There were statistical differences between the two groups in terms of Masaoka-Koga (MK) staging and TNM staging (P<0.05), but no significant differences were found in terms of age, gender, body mass index (BMI), smoking history, alcohol consumption history, history of diabetes, hypertension, maximum tumor diameter, capsule integrity, presence of myasthenia gravis, or surgical methods (P>0.05). Kaplan-Meier survival analysis showed that postoperative adjuvant radiotherapy significantly improved disease-free survival (DFS, P<0.0001) and overall survival (OS, P=0.003). Multivariate Cox regression analysis revealed that MK staging (P<0.01, HR=3.694, 95%CI: 2.018-6.765) and postoperative adjuvant radiotherapy (P<0.01, HR=0.143, 95%CI: 0.074-0.277) were independent risk factors for DFS in thymoma patients. Additionally, MK staging (P<0.01, HR=6.338, 95%CI: 2.362-17.006), postoperative adjuvant radiotherapy (P<0.01, HR=0.096, 95%CI: 0.034-0.275), and capsule integrity (P=0.014, HR=2.930, 95%CI: 1.244–6.902) were identified as independent risk factors for OS. Conclusions Postoperative adjuvant radiotherapy can significantly improve the DFS and OS of patients with completely resected Type B2 thymoma.