Background: The Geriatric 8 (G8) questionnaire has been validated predominantly in Western populations as a screening tool to identify vulnerable older adults with cancer who would benefit from comprehensive geriatric assessment (CGA). Given the paucity of evidence of the performance of this tool in a multi-ethnic Asian population, there is a need to determine whether the established cut-off score of 14 should be adjusted for improved performance in this population of older adults. Methods: Prospective cross-sectional study was done in older adults aged ≥ 65 years in the outpatient setting of an academic tertiary cancer center, the National University Cancer Institute, Singapore (NCIS). G8 questionnaire and CGA were conducted for eligible patients. The performance of the G8 screening tool in identifying patients who would benefit from a CGA was evaluated using receiver operating characteristic (ROC) curve analysis: area under the curve (AUC), sensitivity (Sn), and specificity (Sp). Results: 180 participants (mean age 74 years) were included in the study. 40.5% were female. 90% were Chinese, 7% were Malay, 2% were Indian. 57.8% were pre-frail and 12.8% were frail. The top five cancers in our study population were colorectal (30%), lung (25%), head and neck (12%), upper gastrointestinal (10%) and gynecological (7.0%). ROC analysis showed an AUC of 0.73 (95% CI 0.65 – 0.80) with an optimal cut-off score of 13 (Sn 71.7%, Sp 74.0%). Conclusions: G8 performed well in identifying older adults with cancer who would benefit from a CGA, in a multi-ethnic Asian population. In our cohort, we found that a slightly lower cut-off score of 13 performed better, and should be taken into consideration as part of daily oncology practice in Asia. Future research efforts should go into examining the biological aspects of frailty in this population.