Acute pulmonary embolism is a fatal and unusual disease in children. The major cause of pulmonary embolism is venous thromboembolism. In children, two-thirds of venous thromboembolisms are caused by central venous lines. Although the incidence of venous thromboembolism in adults is much higher than that in children, venous thromboembolism has been increasingly recognized in the pediatric population. Further, the treatment has remarkably improved. We describe both a boy and his father who presented acute pulmonary embolism caused by obesity, sedentarism, and other underlying causes. The boy presented a large pulmonary embolism and was treated with enoxaparin from day 2 of admission to day 15, coumadin from day 2 to day 6, and warfarin from day 11 to day 16. The patient recovered uneventfully and was discharged in a good general condition. He was continued on warfarin treatment.