Pretreatment hematologic abnormalities have been reported to have prognostic value in patients with solid tumors. The aim of our study was to determine the prevalence of abnormalities in the hematologic profile in patients with colorectal cancer before treatment and to evaluate if such a profile could be used for prognostic evaluations. We identified all patients in Cancer Center of Sun Yat-Sen University who were diagnosed as colorectal cancers between May 2005 and August 2009. All subjects were investigated regarding levels of white blood cells, platelets, and hemoglobin concentration. Survival was compared by using the log-rank test on the Kaplan-Meier life table. Multivariate Cox regression analysis was used to evaluate if the pretreatment hematologic profile was independent prognostic factor. We identified 363 patients with colorectal cancer and 315 patients with benign diseases for the final analysis. The percentages of leukocytosis, anemia, and thrombocytosis were significantly higher in colorectal cancer patients than in patients with benign diseases. Univariate analysis showed that advanced tumor stages, leukocytosis, anemia, thrombocytosis, and low histological grade were all significantly associated with shorter survival. The multivariate Cox analysis revealed that low histological grade, tumor stage, pretreatment anemia, and thrombocytosis remained independent prognostic variables for survival. The cumulative effect of anemia and thrombocytosis yielded shorter survival. Anemia and thrombocytosis can be considered as useful prognostic markers in patients with colorectal cancer.