Anemia is common in patients following gastrectomy. The purpose of this study was to document causes of anemias developing during the post-gastrectomy period and to determine the importance of complete blood count parameters on types of anemia. A total of 72 patients (23 women and 49 men) who had previously undergone gastrectomy in the past and who were admitted for the evaluation of anemia were enrolled in study. The patients who were evaluated and treated for anemia in the post-gastrectomy period were excluded. Iron deficiency anemia was present in 68 (94.4%) of 72 gastrectomized patients with anemia. Deficiencies of vitamin B12 and folate were present in 57 (79.2%) and in three patients, respectively. The most common cause of anemia was the combination of iron and vitamin B12 deficiencies. Iron deficiency was present in the majority of patients, followed by vitamin B12 deficiency in frequency. In all combinations of iron deficiency, the values of mean cell hemoglobin and mean cell hemoglobin concentration were either normal or low. In cases who had low white blood cell and platelet counts vitamin B12 deficiency was frequent, while in cases who had high numbers of white cells or platelets iron deficiency was more frequent. In conclusion, gastrectomized patients should be followed for anemia and treated appropriately based on the cause of anemia.