Global childhood obesity increased more than 8-fold over 40 years, inducing a very large personal, societal, and economic burden. Effects of available treatments are less than satisfactory; therefore, effective prevention is of high priority. In this narrative review, we explore preventive opportunities. The available evidence indicates large benefits of improving nutrition and lifestyle during early life, such as promoting breast-feeding and improving the quality of infant and early childhood feeding. Promoting healthy eating patterns and limiting sugar-containing beverage consumption from early childhood onwards are of great benefit. Regular physical activity and limited sedentary lifestyle and screen time alone have limited effects but are valuable elements in effective multicomponent strategies. The home environment is important, particularly for young children, and can be improved by educating and empowering families. School- and community-based interventions can be effective, such as installing water fountains, improving cafeteria menus, and facilitating regular physical activity. Reducing obesogenic risk factors through societal standards is essential for effective prevention and limiting socioeconomic disparity; these may comprise food, drink, and physical activity standards for day cares and schools, general food quality standards, front-of-pack food labeling, taxation of unhealthy foods, restriction of food advertisements to children, and others. Effective prevention of childhood obesity is not achieved by single interventions but by integrated multicomponent approaches involving multiple stakeholders that address children, families, and societal standards. Pediatricians and their organizations should be proactive in supporting and empowering families to support their children's health, and in promoting societal measures that protect children.