OBJECTIVE: Previous studies have reported conflicting results regarding the association between the Geriatric 8 (G-8) geriatric screening tool and prognosis in patients with cancer. This meta-analysis aimed to evaluate the prognostic value of the G-8 score in patients with cancer. METHODS: PubMed, Cochrane Library, Embase, and Medline databases were searched to identify trials exploring the association between G-8 score and prognosis in patients with cancer. Meta-analyses of overall survival (OS) and progression-free survival (PFS) between the high and low G-8 scores were performed. The quality of the included studies was assessed using the Quality In Prognosis Studies tool. RESULTS: A total of 42 studies involving 9053 patients with cancer were included. The prevalence of frailty, evaluated using the G-8 tool across trials, ranged from 27% to 91%. A low G-8 score was associated with poor OS (Hazard ratio [HR] 2.11; 95% CI:1.93-2.31, P <.001) and PFS (HR 1.78, 95% CI,1.55-2.05, P <.001) in patients with cancer. Overall survival were shorter in patients with low G-8 scores than in those with high G-8 scores in digestive system tumors, head and neck cancer, lung cancer, gynecologic tumors, hematologic malignancies, and prostate cancer. The predictive role of the G-8 tool was also confirmed in subgroups with G-8 cutoff values of 9-14. Patients with low G-8 scores had more advanced disease stages and higher ECOG performance status scores. CONCLUSIONS: The prevalence of frailty was high among patients with cancer according to the G-8 geriatric screening tool. Decreased G-8 scores are significantly associated with poor survival in patients with cancer. G-8 is a promising tool for frailty screening.