Résumé : Introduction The concept of frailty extends beyond chronological age. Identifying frailty using a two-step approach, starting with the use of a screening tool (G8) followed by comprehensive geriatric assessment (CGA), may be useful in guiding treatment decisions and follow-up. This study evaluated the association between G8 and CGA, and the risk of 90-day postoperative complications risk, in oncogeriatric patients. Methods Data on geriatric patients with major oncological abdominal surgery was retrospectively collected from our hospital records between 2016 and 2019. Patients with an impaired G8 screening score, who subsequently underwent CGA geriatric screening, were included. Postoperative complications were classified using the Clavien-Dindo classification (CD), and the Comprehensive Complication Index (CCI). The association between the individual components of the geriatric assessment tools and the 90-day postoperative complications risk was analyzed. Results One hundred and twelve patients, aged ≥ 70 years, operated for an intra-abdominal tumor with curative intent, were included. Seventy-six patients (67.9%) presented with an impaired G8, out of whom sixty-six (58.9%) had a CGA performed. On univariate analysis, altered nutritional status assessed by the Mini-Nutritional Assessment-Short Form was the only variable associated with higher postoperative total complication rate ( p = 0 . 01 ). Patients with an impaired G8 had significantly more postoperative complications and higher 1-year mortality rates than patients with normal G8. Fifteen patients (13.4%) had grade III-IVb complications. A CCI > 50 was recorded in 16 patients (14.3%). All-cause 90-day postoperative mortality was 10.7%. Conclusion Identifying an altered preoperative nutritional status, as part of the CGA, in patients screening positive for frailty, is a potentially modifiable risk factor that can enhance preoperative management and optimize treatment decision making. G8 may be a predictive factor for postoperative complications in oncogeriatric patients.