Objective To determine if 24-hour urinary parameters in children with nephrolithiasis across 4 institutions were influenced by body mass index (BMI). Materials and Methods The 24-hour urinary parameters obtained from children with nephrolithiasis between 2000 and 2013 were stratified by BMI percentile ≥85th and Results Overweight and obese patients consisted of 35.4% of the cohort (n = 73). Metabolic abnormalities were present in 130 children (63.1%). The most common abnormality present in the Conclusion Although there is a link between stone formation and BMI in adults, no definitive conclusions have been proven in the pediatric literature. Our study indicates that stone-forming children who are overweight or obese have low urinary volume and elevated uric acid compared to normal-weight stone-forming children.