Anemia remains an essential concern affecting the quality of life and the survival of cancer patients. Although there are different approaches to treating anemia in cancer patients, the number of studies reporting the efficacy of iron replacement in cancer patients is limited. In this study, the efficacy and safety of iron carboxymaltose, a parenteral iron treatment option, in the treatment of anemia, were examined retrospectively. A total of 1102 adult patients who received IV ferric carboxymaltose treatment at Hacettepe Oncology Hospital between 2014 and 2020 were included. The mean hemoglobin change observed at the end of the 12th week was 1.8 g/dL, and the rate of patients with an increase in hemoglobin of 1 g/dL or more was 72.1%. It was observed that the treatment demonstrated effectiveness in patients receiving active cancer treatment in all tumor types. The treatment was generally safe, and no grade 3–5 side effects were observed in the patients included in the study. According to one of the most extensive series published in the literature, iron carboxymaltose is an efficient and safe alternative for cancer patients with iron-deficiency anemia.