Background: Lower respiratory tract infection (LRTI) has long been a leading cause of morbidity and mortality in infancy. Any promising strategies for the prevention of LRTI should be explored extensively and as early as possible. Vitamin D has shown to possess immunomodulatoryproperties and mediate the immune responses to infections. Methodology : A cross-sectional observational study was performed over 177 patients diagnosed with lower respiratory tract infection in the Department of Pediatrics of a tertiary care hospital during the study period of 14 months duration from December 2022 to February 2024 after obtaining consent from the patients.Patients were selected based on clinicaland radiological findings indicative of lower respiratory tract infection, utilizing bothoutpatient department (OPD) and inpatient department (IPD) records while adheringto predefined inclusion and exclusion criteria. Samples were collected for vitamin D measurement using 25(OH) D ELISA. Other investigations like x ray chest and mantoux also done. Results: The data comprised a total of 177 cases, majority of patients' fathers belonged to the lower socio-economic status, accounting for 71 patients (40.1%). The most common symptom was a cough, reported by 174 patients (98.3%) followed by fever, which affected 157 patients (88.7%); cold, reported by 151 patients (85.3%); difficulty in breathing, experienced by 106 patients (59.9%); and other symptoms, which were present in 88 patients (49.7%).The majority of patients were in the insufficient category (12-20 ng/mL), accounting for 118 patients (66.7%) followed by the deficient category (<12 ng/mL), which included 32 patients (18.1%) and sufficient category (21-100 ng/mL) comprised 27 patients (15.3%).Age-wise, 13 patients (40.6%) in the deficient group were aged 6 months to 1 year. Meanwhile, 19 patients (59.4%) in the deficient group were aged1 year to 5 years, compared to 61 patients (51.7%) in the insufficient group and 10 patients (37.0%) in the sufficient group. Gender-wise, 19 male patients (59.4%) were in the Deficient group, compared to 78 male patients (66.1%) in the insufficient group and 18 male patients (66.7%) in the sufficient group. Female patients included 13 (40.6%) in the Deficient group, 40(33.9%) in the Insufficient group, and 9 (33.3%) in the Sufficient group. Although deficient and insufficient levels of Vitamin D are more in male patientscompared to 57 patients (48.3%) in the Insufficient group and 17 patients (63.0%) in sufficient group. Most common diagnosis in deficient group was bronchiolitis 12(37.5%), pneumonia 52(44.1%) in insufficient and sufficient group 52(44.1%) and 11(40.7%) respectively. Sun exposure was adequate in sufficient group while inadequate in both deficient and insufficient group. Conclusion : This study showed children with LRTIs exhibited a higher proportion of vitamin D deficient subjects leading to reduced lung functions. Our research highlights the need to measure blood vitamin D levels in a variety of respiratory conditions in order to start appropriate and prompt treatment interventions that reduce morbidity and death in children under-five. The exposure to the sun and its importance (30 min a day for 5-6 days/week between 10A.M -3 P.M) should be educated. Routine vitamin D supplementation should be advised from birth onwards.