Ghrelin is a major hormone, regulating the energy balance of the body. weight gain is a significant side effect of valproic acid, which has not been clearly identified pathogenetically. The aim of this study was to investigate the effect of valproic acid on ghrelin and its potential effects on weight gain and growth. Each patient and control group consisted of 35 children aged 3 to 15 years. Fasting serum glucose, insulin, C-peptide, leptin, ghrelin, insulin-like growth factor-1, and insulin-like growth factor binding protein-3 levels were measured in patients treated with valproic acid before and at month 6 of treatment. A significant increase in body weight body mass index, height, and height standard deviation scores was observed in all patients after 6 months of treatment. Significant increases in growth velocity and weight gain were observed in the patient group compared with controls at 6 months of therapy. A significant increase in serum ghrelin levels (P <.01) was detected at the same time in the study group. A negative correlation of ghrelin with insulin-like growth factor-1 and insulin-like growth factor binding protein-3 was detected. Serum ghrelin levels were significantly increased (P <.05), and insulin-like growth factor-1 and insulin-like growth factor binding protein-3 levels were significantly decreased (P <.01 and P <.05, respectively) in the prepubertal group at 6 months of treatment, but no significant change was observed in the pubertal group. Consequently, ghrelin levels significantly increase in the prepubertal children treated with valproic acid. The weight gain in using valproic acid may be associated with the increase in ghrelin level in the early treatment period.