Childhood obesity increases the risk of morbidity and mortality in adulthood. The epidemic of childhood obesity has become an important public health issue in Korea. Currently, the overall prevalence of obesity among Korean children and adolescents is approximately 10%, which is 5 times higher than in the late 1970s. In most cases, a positive energy balance (from excessive calorie intake and limited physical activity) combined with a genetic predisposition is considered the major cause of childhood obesity. The evaluation of obese children should focus on possible causes of weight gain, including lifestyle factors and underlying endocrine or genetic abnormalities. The assessment of obesity-related comorbidities, such as hyperglycemia, dyslipidemia, hypertension, and non-alcoholic fatty liver disease, is often needed in obese children, especially those who have a family history of comorbidities. Family-based lifestyle interventions including goal-setting, guidelines for eating habits and physical activity, self-monitoring, and stimulus control are fundamental to the management of childhood obesity. Medications and bariatric surgery are possible choices for patients with severe obesity and comorbidities, although the data on the long-term efficacy and safety of these treatments are limited. This article reviews practical assessments and interventions for childhood obesity.