Background/Aim: The purpose of this study was to compare the prognostic value of preoperative carcinoembryonic antigen (CEA), preoperative CEA/tumor size and postoperative CEA in stage I colorectal cancer. Patients and Methods: We analyzed a total of 305 consecutive stage I colorectal cancer patients who underwent a radical surgery at our Department. The patients were divided into low and high preoperative CEA groups, low and high preoperative CEA/tumor size groups, and low and high postoperative CEA groups according to the optimal cut-off values. Results: Multivariate analysis showed that postoperative CEA was independently associated with OS and DFS. However, the preoperative CEA and preoperative CEA/tumor size were not. Conclusion: The prognostic value of postoperative CEA is better than preoperative CEA and preoperative CEA/tumor size in patients with stage I colorectal cancer. Moreover, the common 5 ng/ml cut-off was not optimal for risk stratification in stage I colorectal cancer.