Context: This review article aims to discuss physical activity during the corona period and its relationship with the physical and mental health of children and adolescents. Methods: A literature search was conducted on the Pub-Med, Wiley, ScienceDirect, and Springer databases from 2020 to 2022 to find related articles scientific. Search engines were searched on September 7, 2022, using the following keywords: Exercise and children and adolescents and COVID-19, physical activity and children and adolescents and COVID-19, sport and children and adolescents and COVID-19, physical activity and children and adolescents and COVID-19 and physical and mental health. Results: The present findings revealed a decline in physical activity levels in children and adolescents during the COVID-19 pandemic. These reductions were associated with various physical and mental health problems. It seems there is a difference in the prevalence of insufficient physical activity across genders, regions, and countries. Conclusions: Restrictions on mobility, social distancing, or closure of schools, clubs, and recreational centers, although an effective measure against the spread of COVID-19, have caused an increase in sedentary behavior, and so the incidence of numerous mental and physical health problems. Therefore, these limitation periods should be shortened as much as possible.