Introduction: Vitamin D deficiency is a prevalent nutritional shortfall and a significant factor contributing to nutritional and growth challenges in infants, particularly those from lower socioeconomic backgrounds. This study primarily aimed to ascertain the prevalence of vitamin D deficiency in infants, and secondarily to examine the relationship between vitamin D levels in infants and their mothers. Material and Methods: Conducted as a prospective, observational study at an Indian hospital, this research included children under one year of age and their mothers. Participants were recruited during well-child and sick-child visits following the acquisition of written, informed consent. Exclusion criteria were major congenital malformations and liver or kidney dysfunction. A serum vitamin D level below 20 ng/mL was classified as deficient. Results: The study included 178 infants and 178 mothers. Of the infants, 79% were neonates, and 21% were older infants. Vitamin D deficiency was identified in 72.78% of the infants and 84% of the mothers, with nearly half of both groups experiencing severe deficiency. Logistic regression revealed a positive correlation between maternal and infant vitamin D levels (r=0.737, p<0.001), as well as associations with neonatal age and low socioeconomic status. Hyperphosphatemia and hypocalcemia were common biochemical abnormalities observed. Conclusion: Vitamin D deficiency was prevalent in 74% of the infants studied. Key factors associated with infant vitamin D deficiency included neonatal age, lower socioeconomic status, and maternal vitamin D deficiency.