Childhood cancer survivors are at increased risk for future health problems. As such, physical activity (PA) has been targeted as a health promotion priority in child and adolescent cancer survivors. Research indicates that a large portion of pediatric survivors do not meet PA recommendations. Using Bronfenbrenner's ecological theory as a framework, this review presents a conceptual model to explain child and adolescent survivors' PA. The model considers predictors of PA across six domains: (1) demographic; (2) medical; (3) cognitive/emotional; (4) behavioral; (5) social/cultural; and (6) environmental. A structured literature review found 14 empirical articles examining those predictors of PA among child and adolescent cancer survivors. Much existing research is cross-sectional, but suggests multiple factors work together to encourage or discourage PA among survivors of child/adolescent cancer. The conceptual model, which is based in empirical findings to date, can be used to understand the process through which PA is promoted and maintained, to inform the development of empirically-supported clinical interventions, and to guide future research objectives and priorities.