Background: The standard treatment in the metastatic colorectal cancer consists of 5-FU based infusional regimens. However, with oral fluoropyrimidines, equal tumor responses may be obtained. Capecitabine causes macrocytosis of the cells by inhibition of DNA synthesis. In this context, a relationship was found between mean corpuscular volume (MCV) and response to therapy in breast cancer patients treated with Capecitabine, but whether this relationship also pertains in colorectal cancer has not been established. Materials and Methods: A total of 102 metastatic colorectal cancer patients treated with a oxaliplatin (XELOX)+/- Bevacizumab combination were retrospectively evaluated. Patients were randomized into three groups. Hematological parameters (MCV, MPV, PCT, PLT, NLR) were recorded retrospectively, before treatment and after 3 cycles of chemotherapy. Results: After three cycles of therapy, 20 (19.6%) patients had progressive disease (PD), 41 (40.1%) had stable disease (SD), and 41 (40.1%) demonstrated a partial response (PR). In 62 (60.7%) treatment was with capesitabin plus XELOX therapy, and in 40 (39.2%) it was XELOX-Bevacizumab combination therapy. There was no difference among three groups before the treatment in terms of MCV, MPV, PCT, PLT, and NLR. MCV showed significant increase in chemotherapy response groups (PR and SD). In addition, a significant decrease was observed for platelet count in chemotherapy response groups. While NLR decrease was seen in only a PR group, PCT decrease was observed in all three groups. PCT and PLT values were higher in patients receiving Bevacizumab. Conclusions: PLT, PCT, MPV, and NLR values were decreased due to Capecitabine-based chemotherapy, however MCV was increased. PCT and PLT values were higher in patients who received Bevacizumab than those who did not. MCV, PLT, and NLR can be considered as important factors in predicting response to colorectal carcinoma treatment.