Myosteatosis has emerged as a promising prognostic biomarker for survival outcomes in patients with advanced cancer. However, recent research has yielded conflicting results on the association between myosteatosis and survival in patients treated with immune checkpoint inhibitors (ICIs). Therefore, we performed this systematic review and meta-analysis to evaluate the association between myosteatosis and survival outcomes in patients treated with ICIs. We conducted a systematic review using Pubmed, Web of Science, and Scopus databases for studies published until June 10, 2024. This protocol was registered in the PROSPERO database (Registration Number: CRD42023466337). We performed the meta-analyses with the generic inverse-variance method with a random effects model. Eleven studies involving 1362 patients were included. The pooled analysis showed that patients with myosteatosis had a significantly higher risk of death compared to patients without myosteatosis (HR: 1.61, 95% CI: 1.23-2.12, p<0.001). Subgroup analysis revealed this association was stronger in melanoma patients (HR: 2.07, 95% CI: 1.09-3.94, p=0.030). Furthermore, patients with myosteatosis had an increased risk of progression or death than those without myosteatosis (HR: 1.31, 95% CI: 1.05-1.64, p=0.020). Myosteatosis is associated with a higher risk of death in ICI-treated patients. Further research in larger cohorts is needed to standardize the definition of myosteatosis as well as the true mechanistic association between myosteatosis and survival in patients treated with ICIs.