Three infants aged between 38 days and 43 days all presented with poor weight gain, hyponatremia, hyperkalemia, and were diagnosed as having urinary tract infections, which were accompanied by urinary tract malformations in our cases. Hydration and infection treatments were given. A few days after admission, hormonal studies revealed normal cortisol and 17-hydroxy progesterone levels and markedly high aldosterone levels, thus the patients were diagnosed as having transient pseudohypoaldosteronism. After the proper treatment was given, the transient pseudohypoaldosteronism resolved. In conclusion, when an infant with urinary tract infection or malformation has electrolyte abnormalities, pediatricians should consider the diagnosis of transient pseudohypoaldosteronism.