Nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH) is a hepatic disease associated with metabolic syndrome. In recent years, pediatric NAFLD has increased in line with the increased prevalence of pediatric obesity. The estimated prevalence of pediatric NAFLD is 2.6-9.6%. With regard to the pathogenesis of NAFLD/ NASH, the "two-hit" or "multiple-hit" hypothesis is widely accepted, and many genetic and environmental factors are associated with the development of NAFLD/NASH. Liver biopsy is regarded as the gold standard for the diagnosis of NAFLD/NASH. Pediatric NAFLD has different histopathological characteristics from those of adult NAFLD. Although pharmacotherapy has been studied in clinical trials, lifestyle modification by diet and exercise remains the mainstay of treatment for NAFLD/NASH.