© 2017 AAB/1. BACKGROUND: Preoperative anemia prevalence among colorectal cancer (CRC) patients is high and may adversely influence postoperative outcome. This study assesses the efficacy of a preoperative anemia managing protocol in CRC. STUDY DESIGN AND METHODS: This was a retrospective analysis of consecutive CRC resections at two Spanish centers (January 2012 to December 2013). Preoperative anemia was defined as a hemoglobin (Hb) level of less than 13 g/dL and treated with intravenous iron (IVI) or standard care (oral iron or no iron). Red blood cell transfusion (RBCT) requirements was the primary outcome variable. Postoperative infection rate and length of hospital stay (LOS) were secondary outcome variables. Patients were managed with a restrictive transfusion trigger (Hb < 8 g/dL). Infection was diagnosed clinically and confirmed by laboratory, microbiologic, and/or radiologic evidence. RESULTS: Overall, 322 of 571 patients (56%) presented with anemia: 232 received IVI and 90 standard care. There were differences in RBCT rate between no anemia and anemia (2% vs. 16%; p < 0.01), but not in postoperative infections (19% vs. 22%; p = NS) or LOS. Compared to those on standard care, anemic patients on IVI presented with lower Hb (10.8 g/dL vs. 12.0 g/dL; p < 0.001) at baseline, but similar Hb on day of surgery and Postoperative Day 30. There were no between-group differences in RBCT rates (16% vs. 17%; p = NS), but infection rates were lower among IVI-treated patients (18% vs. 29%; p < 0.05). No relevant IVI-related side effects were recorded. CONCLUSION: Compared to standard care, IVI was more effective in treating preoperative anemia in CRC patients and appeared to reduce infection rate, although it did not reduce postoperative RBCT.