BACKGROUND: The aim of the study was to investigate the association among elevated serum ferritin, metabolic syndrome (MetS) and 'elevated alanine aminotransferase (ALT) levels beyond healthy-range limits' in children and adolescents. METHODS: We analyzed data from 4855 subjects (2579 male) aged 10-19 who participated in the Korea National Health and Nutrition Examination Survey (KNHANES) (2007-2012). RESULTS: The prevalence of MetS and 'elevated ALT' tended to increase with an increase in the serum ferritin quartile (p-value for trend: all <0.05). The odds ratios (ORs) for MetS in serum ferritin quartile-Q4 compared to ferritin quartile-Q1 was 1.59 (1.01, 2.55) in females after adjusting for age, body mass index (BMI), and insulin resistance. The ORs for 'elevated ALT' in ferritin quartile-Q4 compared to ferritin quartile-Q1 were 4.45 (2.18, 9.10) in male and 3.10 (1.70, 5.66) in female subjects after adjusting for other covariates. CONCLUSIONS: The independent association between elevated serum ferritin and MetS (or 'elevated ALT') begins in children and adolescents.