Background: Children with Vitamin D deficiency are at an increased risk for acute respiratory tract infections (ARTIs). Till now, few studies have been conducted on the use of Vitamin D against ARTIs, but the findings are conflicting and not conclusive. Aim: The aim was to study the effect of Vitamin D supplementation in the prevention of recurrent ARTIs in under‑five children. Methods: In this prospective study, a total of 310 children aged between 1 and 5 years diagnosed with ARTI were included. They were randomized into two groups: Group A (oral Vitamin D 120,000 IU with standard treatment; n = 155) and Group B (placebo with standard treatment only; n = 155). Follow‑up of the patient was done every month for a period of 6 months to document the recurrence of acute attacks of ARTI. R version 3.6.0 software was employed to analyze the data. Results: Twelve children (3.9%) in Group B were unable to follow‑up, and hence, 143 were considered for statistical analyses in that group. Among the 298 children, 63.7% were males and majority (25.5%) of them were in the age group of 11–20 months. Cough (96%), fever (93%), and rhinitis (85.2%) were the commonly encountered symptoms. On day 4th (after Vitamin D supplementation), majority in Group A (40%) had recovered completely compared to Group B (5.6%). Within 5 days, Group A patients were 7 times (odds ratio: 6.97, Confidence interval: 3.5–13.8; P < 0.0001) more likely to have a high recovery rate compared to Group B patients. The proportion of patients with minimal attacks (three or four) of ARTI was significantly less in Group A (7.7%) compared to Group B (32.4%; P < 0.001). Conclusions: Children with Vitamin D supplementation had better and rapid recovery from ARTIs and reduced frequency of ARTI attacks.