Coronavirus disease 2019 (COVID-19) is a global health problem that can result in serious complications. The aim of this study was to investigate the prevalence and clinical importance of vitamin D deficiency in children with COVID-19. This study includes 40 patients who were diagnosed to have COVID-19 and hospitalized with the real-time reverse transcription polymerase chain reaction method, 45 healthy matched control subjects with vitamin D levels. The age of admission, clinical and laboratory data, and 25-hydroxycholecalciferol (25-OHD) levels were recorded. Those with vitamin D levels which are below 20 ng/ml were determined as Group 1 and those with ≥20 ng/ml as Group 2. Patients with COVID-19 had significantly lower vitamin D levels 13.14 μg/L (4.19-69.28) than did the controls 34.81 (3.8-77.42) μg/L (p < .001). Patients with COVID-19 also had significantly lower serum phosphorus (4.09 ± 0.73 vs. 5.06 ± 0.93 vs. (U/L) (p < .001)) values compared with the controls. The symptom of fever was significantly higher in COVID- 19 patients who had deficient and insufficient vitamin D levels than in patients who had sufficient vitamin D levels (p = .038). There was a negative correlation found between fever symptom and vitamin D level (r = -0.358, p = .023). This is the first to evaluate vitamin D levels and its relationship with clinical findings in pediatric patients with COVID-19. Our results suggest that vitamin D values may be associated with the occurrence and management of the COVID-19 disease by modulating the immunological mechanism to the virus in the pediatric population.