The risk of thromboemboli is increased in patients with cancer, and this is precipitated by the chemotherapeutic agents. Bevacizumab is an anti-vascular endothelial growth factor monoclonal antibody and has an importance in the treatment of metastatic colon cancer. The association between bevacizumab, which is demonstrated to increase the risk of thromboemboli, and mean platelet volume (MPV), which is a marker of thrombocyte function, has been investigated within study. A total of 74 patients with metastatic colon cancer were included in the study and the levels of platelets (PLTs), MPV, and platecrit (PCT) values were recorded in SPSS 16.0 program both at baseline and at the >third month. There were significant decreases in 3 parameters (PLT, MPV, and PCT) during the treatment period with bevacizumab (P = .009, P = .001, and P = .000, respectively). Unlike cases with thrombosis, there is a significant decrease in MPV in combination treatments with bevacizumab.