Background: The pathophysiology of cancer-related anemia is multifactorial, including that of chemotherapy-induced anemia (CIA). The guidelines are not consistent in their approach to the use of intravenous (IV) iron in patients with cancer as part of the clinical practice. Materials and methods: All randomized controlled trials that compared IV iron with either no iron or iron taken orally for the treatment of CIA were included. We excluded trials if erythropoiesis-stimulating agents (ESAs) were used. The primary outcome was the percentage of patients requiring a red blood cell (RBC) transfusion during the study period. The secondary outcomes included the hematopoietic response (an increase in the Hb level by more than 1 g/dL or an increase above 11 g/dL), the iron parameters and adverse events. For the dichotomous data, risk ratios (RRs) with 95% confidence intervals (Cis) were estimated and pooled. For the continuous data, the mean differences were calculated. A fixed effect model was used, except in the event of significant heterogeneity between the trials (p < 0.10; I2 > 40%), in which we used a random effects model. Results: A total of 8 trials published between January 1990 and July 2021 that randomized 1015 patients fulfilled the inclusion criteria. Of these, 553 patients were randomized to IV iron and were compared with 271 patients randomized to oral iron and 191 to no iron. IV iron decreased the percentage of patients requiring a blood transfusion compared with oral iron (RR 0.72; 95% CI 0.55−0.95) with a number needed to treat of 20 (95% CI 11−100). IV iron increased the hematopoietic response (RR 1.23; 95% CI 1.01−1.5). There was no difference with respect to the risk of adverse events (RR 0.97; 95% CI 0.88−1.07; 8 trials) or severe adverse events (RR 1.09; 95% CI 0.76−1.57; 8 trials). Conclusions: IV iron resulted in a decrease in the need for RBC transfusions, with no difference in adverse events in patients with CIA. IV iron for the treatment of CIA should be considered in clinical practice.