This study investigated the impact of residential radon exposure on human cancers (i.e., lung cancer and childhood leukemia) through a systematic review and meta-analysis of case-control studies. A total of 9724 articles obtained from electronic databases were assessed; however, only 55 case-control studies were eligible after manually screening and eliminating unnecessary studies. The causal associations were addressed by determining the meta-analysis's estimated size effects (i.e., ORs/RRs) of the meta-analysis. Residential radon was revealed to significantly increase the incidence of lung cancer and childhood leukemia with pooled ORs of 1.38 [1.19; 1.60] (I-2 = 90%; p < 0.00001) and 1.43 [1.19; 1.72] (I-2 = 0% and p = 0.51), respectively. In addition, subgroup analyses were performed to reduce the heterogeneity of the initial meta-analyses. The results provided strong evidence that inhaling radon in the indoor environments is closely associated with the development of lung cancer and childhood leukemia in patients living in Europe and areas with high radon levels (>= 100 Bq/m(3)).