Objective: Cathelicidin is a crucial antibacterial peptide that is produced in the urinary system and is induced by vitamin D. In order to distinguish between lower and upper urinary tract infections (UTIs), the association between cathelicidin levels and vitamin D levels was examined in this study. Material and Methods: We analyzed complete blood count, biochemistry profile, C reactive protein (CRP), 25 hydroxyvitamin D, serum cathelicidin levels of pre-treatment children aged 0-18 years who were diagnosed with a UTI in the Pediatric Emergency Room. Results: A total of 72 children (36 healthy and 36 patients) were included in the study. The mean age of the participants was 83.8±66.22 months, with 40 (56%) female and 32 (44%) male. Our patient group had higher white blood cell, neutrophil, and CRP levels than our control group (p=0.050). There was no significant difference in cathelicidin levels (5.7±3.7, 9.6±10.9; p=0.810) or vitamin D levels (23.3±9.5, 25.9±12.5; p=0.795) between patients with lower and upper UTI. We found a positive correlation between vitamin D and cathelicidin levels in the control group (r:346, p=0.030). There was no statistically significant difference in cathelicidin levels between patients with upper UTI and the control group (p=0.054). Conclusion: Although there was no significant relationship between vitamin D and cathelicidin levels in children with urinary tract infections, a weak but positive correlation exists between vitamin D and cathelisidin in healthy children.