Aim: To compare the levels of vitamin D in children with severe early childhood caries (SECC) and children without caries and to determine the association of vitamin D deficiency and SECC. Materials and methods: A total of 30 children each from case (with caries) and control group (without caries) of age between 3 and 6 years were selected from the Department of Pedodontics and Preventive Dentistry, Faculty of Dental Sciences, SGT University, Gurugram. Caries status of the children was recorded using decayed, extracted, and filled teeth (deft) index. Blood samples for serum 25(OH) vitamin D were taken from each child. All the data collected were compiled and subjected to appropriate statistical analysis. Results: Case group has mean serum 25(OH) vitamin D level of 12.19 ng/mL [4.37 standard deviation (SD), 95% confidence interval of 10.5–13.8] and control group has mean serum 25(OH) vitamin D level of 20.11 ng/mL (4.12 SD, 95% confidence interval of 18.56–21.65). When the mean levels of serum 25(OH) vitamin D were compared between case and control groups, there was a statistically significant difference (p-value <0.0001). Simple linear regression in case group shows statistically significant inverse correlation between vitamin D levels and SECC (p-value<0.0001). Conclusion: Our results showed that vitamin D deficiency is risk factor both for incidence of dental caries and for its severity in children. Clinical significance: Vitamin D deficiency is an important modifiable risk factor for dental caries in children. Hence, by supplementing vitamin D in children and preventing the deficiency of vitamin D, dental caries can be prevented.