Purpose: We did a retrospective study to understand the prognostic effects of preoperative blood transfusions in stomach cancer surgery. Materials and Methods: Data for 1,360 patients who underwent gastrectomy for stomach cancer between 2001 and 2009 were retrospectively reviewed. We analyzed factors that affect preoperative transfusion and clinicopathologic features. We also analyzed 5-year and overall survival rates of the transfusion and non transfusion subgroups. Results: Sixty patients (4.4%) required blood transfusion within the preoperative period. The transfused group included patients who took aspirin or clopidogrel (P<0.001), with more advanced T stages (P<0.001), with more advanced nodal metastasis (P=0.00), and with more advanced stages (P=0.00) than the non transfusion group. On multivariate analysis, preoperative transfusion was a statistically significant negative influence on 5-year survival and overall survival rates (58.2% vs 79.9% (P=0.00), 58.2% vs 76.8% (P=0.00)). Applying Cox-regression analyses, blood transfusion did appear to have an effect on prognosis and on 5-year and overall survival rates. Conclusions: We found a direct negative relation between preoperative transfusion and long term prognosis in patients receiving gastric cancer surgery.