Background: Lower respiratory tract infections (LRTIS) remain among of the most important causes of morbidity and mortality among children. Several studies have associated vitamin D deficiency with an increased risk of LRTIS, and vitamin D supplementation has been proposed as a possible preventive measure against RTIS in children. The aim of this work was to assess the association between vitamin D level and acute lower respiratory tract infections in children. Methods: This Cross-Sectional Study was conducted on 67 Children with acute lower respiratory tract infections were admitted to Chest and Allergic Diseases Unit, Pediatric department, Zagazig University Hospital during the period from March to October 2018. Complete clinical examination with special concern on chest examination, anthropometric measurement, signs of respiratory distress depended on child's age Results: This study included 67 children with acute lower respiratory tract infections, their age ranged from 6months to 10 years. (31.3%) of the study group had pneumonia, (29.9%) bronchopneumonia, (23.9%) bronchiolitis, (9%) pleural effusion and (6%) had hydro-pneumothorax. Regarding disease severity, (41.8%) had mild disease and (58.2%) had severe disease. According to vitamin D level, it was deficient in (49.3%), insufficient in (16.4%) and sufficient in (34.3%). There was a statistical significant negative correlation between vitamin D levels with disease severity. Also, vitamin D was more sufficient in ward patients more than PICU. Conclusion: It was concluded that decreased vitamin D levels in children with ALRTIS might play an important role in disease and as a risk factor in severity, recurrence of ALRIS in children.