Valproate sodium (VPA) is a commonly used antiepileptic drug. However, various side effects, including liver dysfunction, thrombocytopenia, anorexia, hyperammonemia, and pancreatitis have been reported in association with the administration of VPA. Recently, renal Fanconi syndrome associated with VPA treatment has occasionally been reported. However, the mechanisms and detailed characteristics of this adverse effect remain unknown. We herein report three cases of Fanconi syndrome associated with VPA treatment. All of these patients were severely disabled children, who had been previously treated with multiple antiepileptic drugs, and also required tube feeding. The possible risk factors of Fanconi syndrome in these three cases were similar to those previously reported in the literature. In addition, all three patients developed Fanconi syndrome after the onset of bacterial infections. Before developing Fanconi syndrome, hypouricemia was observed in all three and an increased urinary level of beta2 microglobulin (beta2MG) was also noted in one of the patients. None of these patients had hypophosphatemia. Two patients had an appropriate serum VPA level, while the other had an inappropriately high level. We therefore recommend that severely disabled children receiving multiple antiepileptic drugs and tube feeding be periodically checked for urinary beta2MG and uric acid, especially during the course of any infectious episodes.