The cachexia index is a novel indicator of cachexia, but its prognostic implications for survival outcomes have not been systematically assessed in patients with gastrointestinal cancer. This systematic review and meta-analysis aimed to examine the association between the cachexia index and survival outcomes in gastrointestinal cancer patients. Two independent reviewers searched PubMed, Embase, and Web of Science to identify studies that evaluated the prognostic significance of the cachexia index in patients with gastrointestinal cancer. The prognostic value of the cachexia index was determined by combining the adjusted hazard ratios (HR) and 95% confidence intervals (CI). Thirteen studies were identified, including a total of 4207 patients. Meta-analysis indicated that a lower cachexia index was associated with shorter overall survival (HR 2.18; 95% CI 1.78-2.66) and disease-free survival (HR 1.72; 95% CI 1.50-1.97) in gastrointestinal cancer patients. Further stratified analysis confirmed the significant association between a lower cachexia index and shorter overall survival in different study designs, regions, patients' age, sample sizes, gastrointestinal cancer subtypes, tumor stages, and follow-up duration subgroups. The cachexia index could be utilized as a predictor of overall survival and disease-free survival in patients with gastrointestinal cancer. However, future prospective studies are required to confirm these findings.