Background: The aim of this study was to find that if the red cell distribution width (RDW) or hemoglobin (Hb) level variations had prognostic value in stage III colorectal cancer patients treated with operation and adjuvant chemotherapy. Methods: One hundred and twenty-two patients were included in this retrospective study. All were diagnosed and re-staged as stage III colorectal cancer in Sichuan Cancer Hospital according to the AJCC Cancer Staging Manual, 8 th edition, 2018. The patients received R0 resection before adjuvant chemotherapy. The baseline information, routine blood examination data, pathological outcome and prognostic stature was retracted from the database. Receiver operating characteristic (ROC) curve analysis was utilized to determine the cut-off value, while the survival analyses were performed with Kaplan-Meier curve, the log-rank test and the Cox regression analysis. Results: The chemotherapy-associated hemoglobin change (change between the pre- and post-chemotherapy hemoglobin levels) was identified to be associated with the metastasis (P=0.030). The optimal cut-off point was calculated to be -9.5 by the ROC curve of the hemoglobin change, while the area under the curve was 0.648 (95% CI: 0.524-0.772). The results showed that patients with larger hemoglobin decrease had significantly worse disease free survival (DFS) than those with smaller decrease (P=0.020). Factors associated with DFS in uni-variate COX regression analysis were the number of harvested lymph nodes (P=0.040) and the perineural invasion (P=0.020). The peri-chemotherapy change of hemoglobin level was estimated to have significant effect on patient survival (P=0.010). Conclusions: We concluded that chemotherapy-associated Hb change (change between the pre- and post-chemotherapy) was a DFS prognostic factor for the stage III colorectal cancer patients who underwent operation and adjuvant chemotherapy.