BACKGROUND Thymic carcinoma is a rare tumor. Limited data are available regarding the effectiveness of treatment and the prognosis of thymic carcinoma. The present study aimed to clarify the prognostic factors in patients who underwent resection. METHODS The study retrospectively reviewed 21 patients (15 men, 6 women) with thymic carcinoma who had undergone resection at Niigata University Hospital. RESULTS Masaoka stage was II in 4 patients, III in 9, IVa in 2, and IVb in 6. Histologic subtypes were squamous cell carcinoma in 14 patients, adenocarcinoma in 2, atypical carcinoid in 3, and undifferentiated carcinoma in 2. Histologic grade by degree of differentiation was low in 4 tumors, intermediate in 12, and high in 5. Treatment comprised resection alone in 6 patients and resection along with multimodal therapies in 15. Complete resection was achieved in 14 (67%). Eight patients died of tumor. Recurrence was documented in 7 of 14 patients with complete resection, and 5 received additional treatment. The overall 5-year survival rate was 61.1%, and the disease-free 5-year survival rate was 66.8% for the 14 with complete resection. By multivariate analysis, Masaoka stage and histologic grade were significant independent prognostic factors for overall survival. CONCLUSIONS The surgical outcome of patients with thymic carcinoma depends on the Masaoka stage and histologic grade. Patients with early Masaoka stage and low or intermediate histologic grade had favorable prognoses.