Introduction Vitiligo is a skin condition that appears as white blotches and is brought on by the epidermis losing melanocytes, the cells that give skin its color. Numerous theories have been proposed to explain it, but the exact cause is still unclear. Vitamin D3, an essential vitamin, plays a role in immunological response and may help regulate melanocyte activity. Vitiligo and other autoimmune diseases have been linked to low levels of this powerful immune-modulating vitamin. Moreover, vitamin D3 promotes tyrosinase activity and melanin formation via binding to the vitamin D receptor in melanocytes. The primary objective of the study is to determine if the vitamin D levels are impaired and different in vitiligo patients compared to those in healthy individuals, and the secondary objective is to ascertain the impact of this impairment on the severity and scope of the illness. Methodology This study is a prospective case-control design. Over a 12-month period from March 2024 to March 2025, patients visiting the dermatology outpatient department (OPD) at our tertiary care hospital diagnosed with vitiligo were randomly enrolled as cases. Age- and gender-matched healthy individuals attending the hospital were recruited as controls. There were 40 vitiligo sufferers and 40 control subjects in the study, who were taken as per the cases visiting our OPD. The Vitiligo Extent Tensity Index (VETI) score was used to evaluate the degree of skin involvement in vitiligo patients. In order to evaluate serum vitamin D3 levels using the chemiluminescence method, blood samples were obtained from both cases and controls after informed consent and clearance from the institutional ethical committee. Based on their vitamin D3 levels, individuals were divided into three groups: inadequate (<20 IU), insufficient (20-30 IU), and normal (>30 IU). The mean and standard deviation were computed based on the results. Results The age and gender distribution of the vitiligo patients and the control group in this study did not differ significantly. The gender distribution of the 40 cases and 40 controls was equal, with 50% of the participants being men and 50% being women. The largest percentage of participants (37.5%) were between the ages of 41 and 60, followed by those between the ages of 21 and 40 (35%), 11 and 20 (17.5%), one and 10 (10%). Vitiligo patients had a mean serum vitamin D level of 25.1 ± 10.6 ng/mL, while the control group had a significantly higher level of 37.9 ± 26.0 ng/mL (t value = -2.88 and p = 0.0057, statistically significant). Furthermore, chi-square value = 10.60 and p = 0.0314 indicated a statistically significant correlation between serum vitamin D levels and the degree of vitiligo as determined by the VETI score. The study showed that vitiligo patients had lower vitamin D levels compared to those of healthy subjects, and it also made clear how vitamin D deficiency may affect the severity and extent of vitiligo. Conclusion Vitiligo is recognized as a complex disorder with multiple factors. Melanocytes possess vitamin D receptors, which indicates that vitamin D might be involved in regulating their function. Thus, we investigated the role of vitamin D in the etiopathogenesis of vitiligo. The study indicates an inverse correlation of serum vitamin D3 levels with the degree of vitiligo.