Objective A growing body of evidence supports an association between vitamin D and cardiovascular diseases. Coronary artery bypass grafting surgery is a treatment modality for suitable patients with coronary artery disease; however, patency rates of saphenous vein grafts (SVGs) are low. In this study we aimed to determine the association between vitamin D levels and the SVG disease. Methods The study population included 180 patients who had undergone a primary coronary artery bypass grafting surgery with at least one SVG and later had a control angiography because of clinical indications. Patients were divided into two groups: 100 patients with SVG disease and 80 of them with patent SVG. Results The mean age of 180 patients was 57.4 +/- 8.8 years, and 64.4% of the study population were men. The total number of SVGs was 364, and the mean number of SVGs to each patient was 2.02 +/- 0.61. Vitamin D levels were higher in the patent SVG group than in the SVG disease group (36.2 +/- 10.7 and 21.1 +/- 10.4, respectively; P < 0.001). C-reactive protein levels were significantly higher in the SVG disease group (8.3 vs. 6.5 mg/dl, P = 0.001). In a multivariate regression analysis, current smoking, diabetes mellitus, target artery diameter less than 1.5 mm, bypass time duration, and vitamin D levels remained as independent factors associated with SVG disease. Conclusion Lower vitamin D levels are associated with occlusion of SVGs in patients with coronary artery disease. Copyright (C) 2015 Wolters Kluwer Health, Inc. All rights reserved.