The link between serum vitamin D levels and the extent of coronary artery disease (CAD) and inflammatory markers (C-reactive protein and fibrinogen) was studied in 239 patients who underwent coronary angiography. The Gensini lesion severity score was used for assessing the severity of coronary atherosclerosis. Results found overall vitamin D insufficiency in the study population and the Gensini score was negatively associated with serum vitamin D levels and positively correlated with age, blood pressure, diabetes, hyperlipidemia, and C-reactive protein. Results suggest that vitamin D levels may be a significant predictor for the severity of CAD.