This study examines if bilateral internal thoracic artery (BITA) grafting provides improved outcomes compared with single internal thoracic artery (SITA) grafting, in the modern era, in which diabetes mellitus and obesity are more prevalent. The Society of Thoracic Surgeons database at a single large academic center was reviewed for all consecutive isolated coronary artery bypass grafting patients with two or more distal anastomoses from January 1, 2002, through December 31, 2010. Propensity-adjusted logistic and Cox regression models were used to estimate the effect of BITA on short-term outcomes and long-term survival for diabetic and nondiabetic patients. A total of 3,527 coronary artery bypass grafting operations (812 BITA, 2,715 SITA) were performed. Fewer BITA than SITA patients had diabetes (28.6% vs 44.7% p < 0.001). There was no significant difference in 30-day rates of death, stroke, or myocardial infarction between nondiabetic patients who had BITA vs SITA, or between diabetic patients who had BITA vs SITA. BITA grafting conferred a 35% reduction (95% confidence interval, 12% to 52%, p = 0.006) in the long-term hazard of death equally for nondiabetic and diabetic patients (p = 0.93). Deep sternal wound infection was more common among diabetic than among nondiabetic patients (1.5% vs 0.7%), but was similar within nondiabetic (1.0% vs 0.6%) and diabetic patients (1.7% vs 1.5%) who had BITA vs SITA. Overall, BITA and SITA patients had similar rates of deep sternal wound infection (1.2% vs 1.0%). BITA grafting confers a long-term survival advantage and should be performed whenever suitable coronary anatomy exists and patient risk factors allow an acceptable risk of deep sternal wound infection.