BACKGROUND: The relationship between sarcopenia and postoperative outcomes in patients with gastric cancer remains controversial. This study aimed to investigate the impact of sarcopenia on short-term outcomes after surgery for gastric cancer. METHODS: Patients who underwent surgical treatment for gastric cancer were evaluated in this prospective observational study. Muscle strength, muscle mass, and physical performance were measured before surgery. Diagnosis of sarcopenia was based on the revised European Working Group on Sarcopenia criteria. Postoperative 30-day outcomes, including complications, reoperation, readmission, and operative mortality, were recorded. RESULTS: Sarcopenia was observed in 31 out of 146 patients (21.2%). The overall complication incidence was 31.5%. The postoperative complication rate was higher in the sarcopenic patients compared to the nonsarcopenic patients (54.8% versus 25.2%, P = 0.003). There was no statistically significant difference in terms of surgical complication rates (25.8% versus 14.8%, P = 0.239), although the sarcopenic group had a significantly higher systemic complication rate (38.7% versus 13%, P = 0.003). No statistically significant difference was observed in terms of major complications (3.2% versus 5.2%, P = 1.000). Muscle strength, muscle mass, and physical performance were not identified as independent factors when tested alone at adjusted multivariable analysis. Sarcopenia (Odds ratio: 2.73, 95% CI 1.02-7.52, P = 0.047) and severe sarcopenia (Odds ratio: 4.44, 95% CI 1.57-13.34, P = 0.006) were identified as independent prognostic factors for postoperative complications. CONCLUSIONS: Sarcopenia was associated with postoperative complications after gastrectomy for gastric cancer. Severe sarcopenia may serve as a more robust prognostic indicator. The variation in the complication rates between sarcopenic and nonsarcopenic patients was mainly due to difference in systemic complications rather than surgical complications.