Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide, and is commonly associated with obesity. The spectrum of NAFLD ranges from simple steatosis to nonalcoholic steatohepatitis (NASH) and cirrhosis. Fructose ingestion, visceral obesity, and metabolic syndrome are risk factors for liver fibrosis. NAFLD is characterized by two steps of liver injury: intrahepatic lipid accumulation in the setting of insulin resistance, and inflammatory progression to NASH by oxidative stress and inflammatory mediators. Noninvasive methods (e.g., abdominal ultrasonography) are safe ways to support a diagnosis of hepatic steatosis, but liver biopsy remains the gold standard for accurate diagnosis and staging of NASH. Pediatric NASH often displays a histologic pattern distinct from that found in adults. Lifestyle modification through diet and exercise should be attempted in patients diagnosed with NAFLD.