Background <p>Conditions such as sarcopenia and frailty, which become more prevalent with age, significantly influence the outcomes of older patients with cancer undergoing surgery. The aim of this study was to identify the combined effects of sarcopenia and frailty in predicting postoperative complications and mortality.</p> Methods <p>This retrospective cohort study was conducted at a university hospital from May 2019 to December 2020 and included patients aged ≥ 65 years undergoing intermediate-risk cancer surgery. Sarcopenia was defined according to the Asia Working Group for Sarcopenia 2019 guideline, and frailty was assessed using the Multidimensional Frailty Score (&gt; 5) from comprehensive geriatric assessments. The primary outcome measured was composite postoperative complications, with secondary outcomes including one-year mortality, overall mortality, and total hospital stay.</p> Results <p>We included 553 patients (mean age: 75.6 years). Patients with both conditions (21.1%) or frailty alone (19.3%) experienced significantly higher rates of postoperative complications and mortality than those in the normal group (9.2%) and those with only sarcopenia (14.6%). Multivariate analysis confirmed that frailty alone or both sarcopenia and frailty were independent predictors of adverse postoperative outcomes and increased mortality. Kaplan–Meier survival curves further highlighted the significant impact of the frailty-only and combined sarcopenia-frailty groups on survival.</p> Conclusion <p>Frailty was a strong independent predictor of adverse postoperative outcomes and mortality in older people undergoing intermediate-risk cancer surgery. Sarcopenia alone did not significantly increase this risk, and its coexistence with frailty did not independently amplify the risk beyond frailty itself. Evaluating frailty through comprehensive geriatric assessment might have helped improve surgical risk stratification and perioperative care.</p>