Background The effect of preoperative sarcopenia on postoperative complications and prognosis in patients undergoing gastrectomy for gastric cancer has been controversial. The purpose of this study was to explore the effect of preoperative sarcopenia on postoperative complications and prognosis of patients with gastric cancer through meta-analysis method, providing new ideas for the prognosis study of patients undergoing gastrectomy for gastric cancer. Methods From databases establishment to April 2021, we systematically searched PubMed, Embase, Web of Science, the Cochrane Library, China National Knowledge Infrastructure (CNKI), VIP, WanFang Data, and Chinese Biomedical Literature Database (CBM) to collect cohort studies on the effect of sarcopenia on postoperative complications or prognosis of gastric cancer. Based on the inclusion and exclusion criteria, two researchers independently screened the literature and extracted the data. The Newcastle-Ottawa Scale was used to evaluate the quality of the included studies and Revman 5.3 software was used for the meta-analysis. Result A total of 20 studies (11 prospective cohort studies and 9 retrospective cohort studies) involving 7615 patients were finally included. Meta-analysis showed that: 1) preoperative sarcopenia significantly increased the risk of overall complications (risk ratio[RR] =2.89, 95% confidence interval[CI]: 1.86, 4.49; P < 0.000 01), serious complications (Clavien-Dindo grade ≥ III, RR = 3.01, 95% CI: 1.73, 5.23; P < 0.000 01), pneumonia (RR =2.64, 95% CI: 1.71, 4.09; P < 0.0001), and obstruction (RR = 3.96, 95% CI: 2.27, 6.90; P < 0.000 01), but did not increase the risk of postoperative delayed gastric emptying (RR = 1.44, 95% CI: 0.63, 3.25; P = 0.38), intra-abdominal infection (RR =2.09, 95% CI: 0.88, 5.00; P = 0.10), and anastomotic leakage (RR = 1.26, 95% CI: 0.69, 2.32; P = 0.45); 2) preoperative sarcopenia reduced the overall survival rate (HR = 1.71, 95% CI: 1.53, 1.91; P < 0.00001). Conclusion Preoperative sarcopenia increased the risk of postoperative complications and reduced the overall survival rate of patients undergoing gastrectomy for gastric cancer. Therefore, for patients with gastric cancer, preoperative risk assessment and active intervention for sarcopenia are necessary to reduce the risk of postoperative complications and improve poor prognosis. Future studies should focus on the effect of preoperative sarcopenia on the quality of life after gastrectomy for gastric cancer.Copyright © 2021. Published by Elsevier B.V.