Thymic epithelial tumors (TETs) consist of a series of neoplasm that differ morphologically and biologically. Due to its rarity and indolent natural history, large-scale prospective trials have been lacking. This study aimed to evaluate long-term clinical outcomes and clinicopathologic features for TET after surgical resection and adjuvant treatments. One hundred patients who received surgery plus adjuvant radiotherapy +/- chemotherapy for TET (Masaoka stage II-IVa) from 1995 to 2005 were retrospectively reviewed. Masaoka staging systems were adopted, and pathologic results were classified according to World health organization (WHO) histologic classification. After surgery, 55 patients were treated with radiotherapy alone, while 45 with radiotherapy and chemotherapy. The median radiation dose was 50.4 Gy (45-63 Gy) and six cycles of chemotherapy, consisting of doxorubicin, cisplatin, vincristine and cyclophosphamide, were applied every 3-4 weeks. Distributions according to Masaoka stage were as follows; stage II (58 patients), III (21) and IVa (21). According to WHO histology, there were A (3), AB (7), B1 (7), B2 (31), B3 (31) and C (21). With a median follow-up duration of 65 months (8-143 months), the 5-year overall survival (OS) and disease-free survival (DFS) rates were 75.7% (89.2, 67.9 and 52.1% in stage II, III and IVa, respectively) and 70.3% (83, 62.4 and 33.6% in stage II, III and IVa, respectively). In multivariate analysis, prognostic factors for OS were age, WHO histology, Masaoka stage, and recurrence, while pleural involvement, WHO histology, and Masaoka stage had significant impacts on DFS. Adjuvant chemotherapy did not alter survival outcomes and recurrence patterns. Pleura was the most common recurrence site (15 patients, 53.6%), and significantly associated with pleural recurrence-free survival. In conclusion, pleural involvement at diagnosis was the important prognostic factor, in addition to WHO histology and Masaoka stage. To prevent pleural recurrence and prolong survival, innovative therapeutic approaches warrant further investigations.