Background: A 2024 study by the National Statistical Office of Mongolia indicate an incidence rate of 38.8 per 100 000 population, with a total of 8169 new cancer cases diagnosed, of which 16.2% are gastric cancers. Notably, 64.4% of these diagnoses are made at advanced stages.2 Surgical intervention remains one of the most effective treatments for gastric cancer. Early-stage surgery confers a 5-year survival rate of 60-80%, whereas late-stage diagnosis reduces this to 18-50%.5 This study aims to investigate the causes, types, and contributing factors of postgastrectomy anemia in patients undergoing surgery for gastric cancer in Mongolia, where no prior study has been conducted on this topic. Methods: This retrospective study analyzed all patients who underwent gastric cancer surgery at the National Cancer Center of Mongolia from 2022 to 2024. Data on demographics, lifestyle factors, clinical signs of anemia, and comorbidities were collected from medical records and confirmed by direct examination. Results: A total of 788 patients who underwent surgery for gastric cancer were included in the study, of whom 70.5% were male and 29.5% female, aged 22–70 years (mean age 46 years). Among the total cases, 461 patients underwent total gastrectomy, 128 had distal gastrectomy with gastrojejunal anastomosis, 39 underwent partial gastrectomy, 3 had gastrectomy with duodenal anastomosis, 5 underwent gastrectomy with esophagogastric anastomosis, and 6 underwent bypass procedures. Conclusions Postoperative monitoring after gastric surgery was insufficient, and there was a tendency for anemia to progress.