Objective. To systematically review studies to provide the pooled estimate of undernutrition among children and adolescents with cancer living in sub-Saharan African countries. Methods. The review followed the recommendations outlined in the PRISMA statement. Online searches were performed on electronic databases such as PubMed, Scopus, Embase, and Hinari; gray literature sources: such as Google, Google Scholar, and university repositories were also searched. A random effect model was used to drive the pooled prevalence, and was reported at a 95% Confidence Interval (CI). Heterogeneity was assessed using subgroup analysis and univariable meta-regression. The effect of each study on the overall prevalence was assessed using leave-one-out sensitivity analysis. In all the models, statistical significance was set at P-value <.05. Result. A total of 623 articles were identified, and 21 articles were retrieved for the final analysis. The overall pooled prevalence of undernutrition was 41.34% (95% CI: 31.64%, 51.04%). The highest prevalence of undernutrition was observed from studies that used Arm Muscle Area (AMC) for age to assess undernutrition: 61.66% (95% CI: 47.59%, 75.72%). The protocol for this review has been registered at PROSPERO (CRD42024510052). Conclusion. The prevalence of undernutrition in sub-Saharan African countries was considerably high. Therefore, policy directions and cost-effective approaches that sustainably address undernutrition among pediatric patients with cancers are needed.