Valproic acid (VPA) is effective for the treatment of many types of epilepsy, but its use can be associated with an increase in body weight. We report a case of nonalcoholic fatty liver disease (NAFLD) arising in a child who developed obesity during VPA treatment. Laboratory data revealed hyperinsulinemia with insulin resistance. After the withdrawal of VPA therapy, our patient showed a significant weight loss, a decrease of body mass index, and normalization of metabolic and endocrine parameters; moreover, ultrasound measurements showed a complete normalization. The present case suggests that obesity, hyperinsulinemia, insulin resistance, and long-term treatment with VPA may be all associated with the development of NAFLD; this side effect is reversible after VPA withdrawal.