Background: coronary artery disease (CAD) remains a leading cause of mortality worldwide. Recent research suggests a potential link between vitamin D deficiency and the pathogenesis of CAD, potentially through mechanisms involving endothelial dysfunction, inflammation, and metabolic regulation. Objectives: To investigate the association between serum vitamin D levels and angiographically confirmed CAD in patients aged 30–70 years. The study also examines the relationship between vitamin D status and CAD severity, considering gender, diabetes, hypertension, smoking status, and specific coronary artery involvement. Methods: This cross-sectional observational study enrolled 100 patients who underwent coronary angiography and were found to have ≥50% stenosis in at least one major coronary artery. Patients with systemic diseases, vitamin D supplementation, or other exclusion criteria were omitted. Demographic, clinical, and laboratory data including serum 25(OH)D levels were recorded. Statistical analyses included t-tests, ANOVA, Chi-square, and Pearson’s correlation, with significance set at p < 0.05. Results: Among 100 patients (75 males, 25 females), 77 were diagnosed with CAD. Mean serum vitamin D level was 19.46 ± 0.83 ng/ml. Patients with normal coronary arteries had significantly higher vitamin D levels (p = 0.01). Vitamin D deficiency was more common among diabetics (p = 0.04) and older patients (p = 0.002), and correlated with higher BMI (p = 0.045). Although no strong correlation was observed between vitamin D levels and CAD severity or number of vessels involved, the right coronary artery (RCA) was most frequently affected, and the left circumflex artery (LCX) showed the most severe stenosis. Conclusion: Vitamin D deficiency appears to be an independent risk factor for the presence of CAD, especially among older, diabetic males. While it does not correlate significantly with CAD severity, its high prevalence among CAD patients highlights the need for public health measures promoting vitamin D supplementation in at-risk populations. Aim of the Study This study investigates the association between vitamin D deficiency and CAD in patients aged 30–70 years. It explores the relationship between vitamin D levels and disease severity in relation to gender, diabetes, hypertension, smoking status, and angiographic findings. It also identifies the coronary arteries most susceptible to stenosis in males and females................ Keywords:........... Vitamin D, Coronary artery disease, Coronary angiography, Serum 25(OH)DI.