Objectives: To evaluate the impact of skeletonized bilateral or single internal thoracic artery (ITA) grafting on the risk of deep sternal wound infection (DSWI) in diabetic patients undergoing off-pump coronary artery bypass grafting (OPCAB). Materials and Methods: A total of 803 diabetic patients undergoing OPCAB surgery from January 2010 to December 2014 were enrolled into this study and assigned to the pSITA group (patients undergoing pedicled single ITA grafting, n = 362), the sSITA group (skeletonized single ITA grafting, n = 295), or the sBITA group (skeletonized bilateral ITA grafting, n = 146). The primary end point was the diagnosis of a DSWI. Results: Eighteen patients developed postoperative DSWI, with an incidence of 2.2%. Patients in the sSITA group had a significantly lower incidence of DSWI than those in the pSITA group (1.0 vs. 3.6%, p = 0.0408). In multivariate logistic regression analysis, the risk of DSWI in the sSITA group was 0.41 times that in the pSITA group. Conclusions: sSITA grafting lowered the risk of DSWI in diabetic patients undergoing OPCAB surgery compared to pSITA grafting. Multicenter clinical trials involving larger sample sizes are needed to determine the merit of pSITA grafting in reducing the risk of DSWI following OPCAB surgery.