AIM: The aim of this study was to investigate the correlation between preoperative systemic immune inflammatory index (SII) and carcinoembryonic antigen (CEA) and postoperative lympho-vascular invasion and TNM stage in patients with colorectal carcinoma. MATERIAL AND METHODS: A total of 153 patients with colorectal cancer admitted to our tertiary hospital between 2014 and 2018 were included in the study. RESULTS: While 71.2% of the patients had low preoperative CEA values, 28.8% had high preoperative CEA values. Lymphovascular invasion rate was found to be significantly higher in patients with high CEA levels than those in low levels (70.4% vs. 39.4%, p=0.002). The percentage of patients with lymphovascular invasion with a high SII (60.0%) was significantly higher than those without lymphovascular invasion (p=0.015). CONCLUSION: In our study, serum CEA and SII index values were found to provide critical information in terms of showing lympho-vascular invasion, which is considered as an independent “bad” prognostic factor in patients with colorectal carcinoma. In conclusion, we consider that CEA and SII index values can be used to determine the prognosis of patients with colorectal cancer.