Cachexia, a multifactorial syndrome, is frequently noticed in cancer patients. A recent study has shown inconsistent findings about the relationship between cachexia and the efficiency of immune checkpoint inhibitors (ICIs). To analyze this disparity, we did a meta-analysis.From the beginning of each database to July 2023, literature describing the association between cachexia and prognosis of ICI-treated patients with solid malignancies was systematically searched in three online databases. Estimates were pooled, and 95% confidence intervals (CIs) were generated.We analyzed a total of 12 articles, which included data from 1407 patients. The combined results of our analysis showed that cancer patients with cachexia had significantly worse overall survival (HR = 1.88, 95% CI: 1.59-2.22, p < 0.001), progression-free survival (HR = 1.84, 95% CI: 1.59-2.12, p < 0.001), and time to treatment failure (HR = 2.15, 95% CI: 1.32-3.50, p = 0.002). These findings were consistent in both univariate and multivariate analyses. Additionally, while not statistically significant, we observed a trend towards a lower objective response rate in cancer patients with cachexia compared to those without cachexia (OR = 0.59, 95% CI: 0.32-1.09, p = 0.093).Poor survival in cachexia patients suggests a negative relationship between cachexia and ICI efficacy. In clinical practice, the existence of cachexia should be estimated to choose individuals who may benefit from ICIs.