Background/objectives: Iron deficiency anemia is common in patients with colorectal cancer and affects postoperative outcomes. Preoperative intravenous iron supplementation corrects anemia effectively; however, the effect on the postoperative clinical course is unclear. The aim of this study was to investigate the effects of implementing a screening program for iron deficiency anemia and correction in patients with colorectal cancer. Methods: This was a retrospective single-institutional quality-assurance study that included patients undergoing elective surgery for colorectal cancer between January 2019 and December 2021. On 1 March 2020, screening for iron deficiency was implemented. Anemia was corrected by intravenous ferricarboyxmaltose. Patients with hemoglobin <7mmol/L and ferritin <30 µg/L or ferritin 30–100 µg/L and TSAT < 0.2 were divided into iron- and non-iron groups. The primary outcome was a change in hemoglobin concentration, and secondary outcomes included blood transfusion, complications, length of stay, mortality, and implementation efficacy. Data from the patients were extracted from digital patient charts and entered into a database. Results: A total of 532 patients were included, of which 177 patients (33.3%) were anemic, 63 were in the iron group, and 114 were in the non-iron group. Adherence to the screening program was 86.3%. Hemoglobin (iron group) increased from a mean of 5.7 mmol/L (SD 0.8) to 6.9 (0.8) mmol/L, p < 0.001. Iron treatment decreased transfusion rates from 27.7% to 9.1%, p = 0.007, and increased the rate of patients without complications from 53.2% to 79.6%, p < 0.001, which held true after controlling for confounding. In addition, 90-day mortality was lower in the iron group; however, this was not significant. Conclusions: Administration of intravenous iron increased hemoglobin, leading to reduced use of blood transfusion and fewer complications.