Background: This study aims to identify risk factors of venous thromboembolism in the patients undergoing thoracic surgery. Methods: A total of 167 patients (107 males, 60 females; mean age 56.7 +/- 16.8 years; range 16 to 81 years) who underwent thoracic surgery between September 2015 and December 2016 were included in this study. D-dimer and C-reactive protein values were analyzed and clinical data recorded. The patients received color Doppler ultrasound and thoracic computed tomography before and after surgery. The risk factors for venous thromboembolism were analyzed. Results: Of the patients, 57 (34.1%) developed venous thromboembolism after thoracic surgery, among whom two patients developed pulmonary embolism and another 55 developed deep vein thrombosis. Age, D-dimer, operation time, and body mass index of venous thromboembolism patients were significantly higher than non-venous thromboembolism patients. There was no significant difference in the C-reactive protein values between the two patient groups. Age, smoking history, operation time, and body mass index were found to be the risk factors of venous thromboembolism. There was a significant difference in the incidence of venous thromboembolism among different surgeries. The patients who underwent esophagectomy had the highest incidence of thrombosis. Conclusion: Age, smoking history, operation time and body mass index are independent risk factors for venous thromboembolism. A special attention should be given to the patients undergoing esophagectomy to prevent the development of venous thromboembolism.