BACKGROUND: There is evidence that nonalcoholic fatty liver disease (NAFLD) increases the risk for dysglycemia in children in cross-sectional studies. However, the extent to which NAFLD may confer the risk for dysglycemia in longitudinal studies remains uncertain. OBJECTIVES: We investigated whether elevated levels of alanine aminotransferase (ALT) as a proxy for NAFLD can serve as a predictor for future dysglycemia among children. METHODS: We performed survival analysis up to 11 years of follow-up on longitudinal data of 510 children with overweight and obesity from the Leipzig Childhood Cohort. RESULTS: Children with overweight/obesity and elevated ALT values had a more than 2-fold increased risk (hazard ratio 2.59, 95% confidence interval 1.49 to 4.50; P < 0.01) for future dysglycemia independent of age, sex and BMI-SDS. CONCLUSIONS: Elevated transaminases are an early predictor for glycemic deterioration. Hence, NAFLD should further be addressed as a risk factor and therapeutic target for the early prevention of type 2 diabetes.