--- - |2 Abstract Background Numerous studies have reported the relationship between systemic immune‐inflammation index (SII) and prognosis in gastrointestinal (GI) cancers, but no consensus has been reached. We aimed to systematically evaluate the prognostic value of SII in patients with GI cancers. Methods Relevant published papers regarding the prognostic value of SII in patients with GI cancers were obtained from a number of electronic databases. The overall hazard ratios and the corresponding 95% confidence intervals (95% CIs) were calculated using a fixed or random effects model to assess the relationship between SII and prognosis through Stata SE 12.0. Results A total of 24 eligible published articles with 9,626 patients were included. From the pooled results, we found that high SII indicated worse overall survival (OS) in patients with GI cancers (HR = 1.52, 95%CI: 1.29–1.74). And patients with high SII had poorer disease‐free survival (HR: 2.28, 95% CI: 1.46–3.10), time to recurrence (HR: 1.70, 95% CI: 1.11–2.30), and recurrence‐free survival (HR: 1.60, 95% CI: 1.19–2.00) when compared with those with low SII values. Conclusions SII might serve as a noninvasive and powerful tool for predicting survival outcome in patients with GI cancers. - Journal of Cellular Physiology, EarlyView.