Background/aim: Gastrointestinal (GI) system cancers are frequent among older adults and it is still difficult to predict which are at increased risk for postoperative complications. Frailty and sarcopenia are increasing problems of older population and may be associated with adverse outcomes. In this study we aimed to examine the effect of sarcopenia and frailty on postoperative complications in older patients undergoing surgery for GI cancers. Materials and methods: Forty-nine patients admitted to general surgery clinic with the diagnosis of gastrointestinal system cancers were included in this cross-sectional study. Frailty status was assessed using the Edmonton Frail Scale (EFS). Sarcopenia was defined due to the EWGSOP2 criteria and ultrasonography was used to evaluate muscle mass. Results: The median age of the patients was 70 (min-max: 65 & ndash;87). Fourteen (28.6%) patients were found to be sarcopenic and 16 (32.7%) patients were frail, and 6 (37.5%) of these patients were also severe sarcopenic (p = 0.04). When the postoperative complications were assessed, time to oral intake, time to enough oral intake, length of hospital stay in the postoperative period were found to be longer in frail patients (p = 0.02, p = 0.03, p = 0.04 respectively). Postoperative complications were not different due to the sarcopenia. Conclusion: Frailty, but not sarcopenia was associated with adverse outcomes in older adults undergoing GI cancer surgery. Comprehensive geriatric assessment before surgical intervention may help to identify patients who are at risk.