Previous studies have shown the protective effects of vitamin D supplementation against urinary tract infection (UTI). However, there are a few contradictory studies on the negative effect of vitamin D supplementation on UTI. Our objective was to establish whether there existed a relationship between serum vitamin D levels and UTIs in children. This study compared the serum 25-hydroxy vitamin D [25(OH)D] levels of children diagnosed with UTIs with those of healthy children (control group). We found a high rate of 25(OH)D deficiency in both the control and case groups (90% and 66.7%, respectively). Therefore, we added the laboratory parameters calcium, phosphate, and parathormone (PTH) to our analysis. We assessed the medical records of 60 patients diagnosed with UTIs and 20 healthy controls. The mean serum 25(OH)D level and PTH level were significantly higher in the patient group than in the control group. The PTH level was significantly lower in the acute pyelonephritis (APN) group than in the control group (p=0.016). Phosphate levels in the APN group were significantly lower than those in the control and cystitis groups (p=0.04, p=0.006 respectively). Because there was no correlation between 25(OH)D level and UTI, we concluded that 25(OH)D had no effect on UTI.