Background: Vitamin D deficiency has emerged as a potential contributor to insulin resistance in type 2 diabetes mellitus (T2DM). This study investigated the relationship between vitamin D status and insulin resistance among patients with T2DM.Methods: A prospective cross-sectional study was conducted at a tertiary care center involving 328 T2DM patients. Serum 25-hydroxyvitamin D levels, glycemic parameters, and insulin resistance (HOMA-IR) were measured. Multiple linear regression analysis was performed to identify independent predictors of insulin resistance. Results: The prevalence of vitamin D deficiency (<20 ng/mL) was 54.6%, with a mean serum level of 20.8 ± 8.4 ng/mL in the study population. A strong inverse correlation was observed between vitamin D levels and HOMA-IR (r=-0.642, p<0.001). Vitamin D deficient patients demonstrated significantly higher HOMA-IR values (6.48 ± 2.82) compared to those with sufficient levels (3.69 ± 1.46, p<0.001). Multiple regression analysis identified vitamin D levels (β=-0.284, p<0.001) as an independent predictor of insulin resistance, along with BMI (β=0.308, p<0.001) and physical activity (β=-0.242, p=0.002). HbA1c levels were significantly higher in vitamin D deficient patients (8.2 ± 1.4%) compared to those with sufficient levels (7.1 ± 0.9%, p=0.002).Conclusion: A significant inverse association exists between vitamin D levels and insulin resistance in T2DM patients. The high prevalence of vitamin D deficiency and its independent association with insulin resistance suggests the potential therapeutic importance of maintaining adequate vitamin D status in T2DM management.