Nocturnal enuresis is a common problem among children. Hypercalciuria has been proposed as an important etiology of bedwetting. We investigated the incidence of hypercalciuria among children with nocturnal enuresis and age- and sex-matched healthy controls. In this case–control study 118 children with nocturnal enuresis and 100 age-, sex-, and educational district-matched healthy controls were recruited. Urine samples were obtained from each subject twice: immediately after awakening and 2 hours later at school. Urinary calcium and creatinine levels were measured and the subjects with a urinary calcium/creatinine ratio more than 0.2 were considered as hypercalciuric. Serum Ca, P, Na, K, and PTH levels were measured for all hypercalciuric subjects. The mean urine calcium to creatinine ratio in the second urine sample was 0.070±0.06 mg/mg and 0.050±0.046, respectively in the case and control groups (P=0.008). There were 12/118 and 3/100 hypercalciuric subjects in the case and control groups respectively (P=0.032). The serum Ca, P, Na, K, and PTH levels were in normal range in all hypercalciuric subjects. In our study there was a significant difference in the frequency of hypercalciuria among children with nocturnal enuresis and healthy controls, so we can suggest adding the measurement of urine electrolytes especially the calcium level in patients with nocturnal enuresis.