Patients and survivors of childhood cancer experience adverse effects related to the disease and its treatment. These adverse effects are associated with both physiological and psychological health. Exercise helps manage the side effects and improve the health outcomes. The objective of this umbrella review is to search the current literature in the context of exercise and physical activity as complementary interventions on pediatric cancer and to provide comprehensive information about the derived health outcomes. A literature search was conducted on the Cochrane, PubMed, and Embase databases for systematic reviews published up to January 2023. Moreover, a hand search of reference lists was performed. We included participants under 19 years of age at diagnosis of any type of childhood cancer, without restriction on the type or phase of treatment, who participated in exercise interventions. The results showed a beneficial impact on fatigue, muscle strength, aerobic capacity, activity and participation levels, psychosocial health, cardiovascular/cardiorespiratory fitness, physical function, bone mineral density, and brain volume and structure, with limited and not serious adverse effects. These findings documented that exercise interventions had a positive effect on many physiological and psychological health outcomes in pediatric cancer patients and survivors.