Abstract: Objective This study was designed to assess the expression levels of bone morphogenic protein-4 (BMP4) in saphenous veins harvested from diabetic patients undergoing coronary artery bypass grafting (CABG), and to investigate its association with in-situ morphological and pathological changes within the venous wall. Methods From January 2013 to December 2014, forty patients with type 2 diabetes mellitus (DM) and risk factors matched non-DM controls (n =40) were enrolled prospectively. Of the 40 DM patients, 24 had noninsulin-dependent diabetes (NIDM) and the remaining 16 had insulin-dependent diabetes (IDM). Segments of saphenous vein without surgical dilatation from these 80 patients were obtained. Vessel wall characteristics were evaluated by hematoxylin-eosin (HE) staining, and the expression and distribution of BMP4 was assessed by Western blot assay and immunohistochemistry analysis. Results The intimal and medial thickness of the saphenous veins harvested from DM patients were higher than those from non-DM controls. Compared with non-DM patients, the expression level of BMP4 was significantly elevated in diabetic veins (P r =0.655, P r =0.684, P r =0.642, P r =0.692, P <0.01). Conclusion The pre-existing intimal and medial hyperplasia were significantly correlated with the high expression levels of BMP4 in saphenous veins harvested from diabetic patients, implying a potential role of BMP4 in the progression of vein graft stenotic diseases in this cohort of post-CABG patients. Future studies were warranted in investigating novel therapeutic strategy targeting at BMP4 for improving long-term vein graft patency.