Introduction: There is a high prevalence of low levels of Vitamin D in the pregnant women. Vitamin D deficiency is accompanied with adverse maternal and neonatal outcomes. Aim and objective: To study perinatal outcomes in vitamin D deficiency, and effect of oral and intramuscular vitamin D3 supplementation in antenatal women on pregnancy outcomes. Materials and methods: It is a randomized prospective comparative cohort study. Antenatal women attending antenatal outpatient department were screened for vitamin D deficiency (<20 ng/dL), and deficient women were divided into two groups and treated with 60,000 IU oral tablet/capsule weekly and injection vitamin D intramuscular 60,000 IU every fortnight for 8 weeks, respectively. Both the groups were compared both before and after supplementation for variables like clinical profile and maternal and fetal outcomes. Results: In our study, vitamin D deficiency <20 ng/dL was found in 90.9%. About half of the women had vitamin D3 less than 10 ng/mL and 40.6% women had their vitamin D3 level between 10 ng/mL and 20 ng/mL. After the oral treatment, mean 25-hydroxy vitamin D level increased to 25.6 ± 1.37 ng/mL and 22.8 ± 2.1 ng/mL at 6 weeks and 12 weeks, respectively, in intramuscular treatment. Mean vitamin D level increased to 26.4 ± 1.85 ng/mL and 29.3 ± 2.08 ng/mL at 6 weeks and 12 weeks, respectively. At 12 weeks, the mean vitamin D level in the IM vitamin D group was higher as compared to the oral vitamin D group. In the present study, no statistically significant differences could be found in the incidence of preeclampsia, GDM, and preterm birth but low birth weight babies were more in the vitamin D deficiency group (13.33%) as compared to the normal vitamin D group (6.67%). Conclusion: There is a high prevalence of vitamin D deficiency in pregnant women in India. Supplementation of Vitamin D as a part of routine antenatal care needs to be established. Both oral and intramuscular vitamin D are effective.