The impact of sarcopenia on the efficacy of immune checkpoint inhibitors (ICI) in gastrointestinal cancer (GIC) patients remains uncertain in clinical practice. Hence, this study aims to investigate the potential correlation between sarcopenia and the clinical outcomes of GIC patients treated with ICIs. To gather pertinent studies, a systematic literature search was implemented across multiple databases, including PubMed, Embase, the Cochrane Library, and Google Scholar. The primary outcomes of interest were overall survival (OS) and progression-free survival (PFS), measured with the hazard ratio (HR). And the secondary outcomes, including disease control rate (DCR), overall response rate (ORR), and adverse events (AE), were evaluated with the odd ratio (OR). A total of 13 articles involving 1294 patients were collected for this analysis. The pooled results revealed that GIC patients with sarcopenia had significantly poorer OS (HR=1.697, 95% CI=1.367-2.106, p<0.001) and PFS (HR: 1.551, 95% CI: 1.312-1.833, p<0.001), and lower ORR (OR=0.594, 95% CI=0.388-0.909, p=0.016) and DCR (OR: 0.553, 95% CI: 0.360-0.850, p=0.007) compared to those without sarcopenia. However, sarcopenia did not increase the incidence of treatment-related adverse events compared with non-sarcopenia (OR=1.377, 95% CI=0.693-2.737, p=0.361). According to subgroup analysis, the association between sarcopenia and the therapeutic effect of ICI on patients with primary liver cancer or gastric cancer was consistent with the above findings. Sarcopenia is significantly correlated with poorer treatment response and worse long-term efficacy in GIC patients treated with ICIs. Moreover, sarcopenia does not increase the incidence of adverse events.