Colorectal cancer (CRC) is the third most common cause of cancer-related death in Europe. The aim of the present study was to elucidate the efficiency of the neutrophil/lymphocyte ratio (NLR), the platelet/lymphocyte ratio (PLR), and the mean platelet volume (MPV) as tools for the preoperative diagnosis of CRC and their usefulness in the follow-up of CRC. A total of 144 CRC patients, as diagnosed by colonoscopy, and 143 age-matched and sex-matched healthy participants were included in the study. Medical records were used to compare preoperative and postoperative data including hemoglobin levels, platelet counts, MPV, NLR, and PLR. NLR, PLR, and MPV were significantly higher in CRC patients preoperatively, compared with healthy participants. Receiver-operating characteristic curve analysis suggested 2.02 as the cutoff value for NLR [area under the curve (AUC): 0.921, sensitivity: 86%, specificity: 84%], 135 as the cutoff value for PLR, (AUC: 0.853, sensitivity: 70%, specificity: 90%) and 8.25 fl as the cutoff value for MPV (AUC: 0.717, sensitivity: 54%, specificity: 76%). Subgroup analysis showed that NLR, PLR, and MPV levels were also significantly higher in nonanemic CRC patients compared with the control group, which is of great theoretical and clinical value for the early detection of CRC. Surgical tumor resection resulted in a significant decrease in NLR, PLR, and MPV. Our results suggest that NLR, PLR, and MPV may be used as easily available additional biomarkers for CRC in screening the general population, as well as in postoperative follow-up.