Consensus has yet to emerge among experts as to whether the radial artery (RA) conduit was superior to the saphenous vein (SV) graft for coronary artery bypass grafting (CABG) in terms of long-term patency. This study aimed to evaluate long-term patency of the RA conduit compared to the SV conduit for off-pump CABG, and to screen the independent predictors of long-term RA graft failure. Patients < 80 years of age with graftable triple-vessel disease undergoing non-emergent, primary, isolated off-pump CABG, using both the RA and the SV conduits, were reviewed. Graft patency, all-cause mortality and repeat revascularization were followed-up. The independent predictors of long-term RA graft failure were identified. A total of 296 out of 320 eligible patients (42 females, 61.3 ± 9.9 years old) received follow-up with an observed period of 93.4 ± 16.5 months. All-cause mortality was 14.5%, and repeat revascularization was conducted on 6 RA grafts and 9 SV grafts. Superior patency of the RA grafts compared to the SV grafts was observed (84.4% versus 78.5%, P = 0.035). Independent predictors of long-term RA graft failure included proximal stenosis of target right coronaries < 90% (OR = 2.35, 95%CI 1.41-5.82) and diabetes mellitus (OR = 1.66, 95%CI 1.17-4.26). The RA graft had a superior long-term patency than the SV graft. Long-term patency of the RA graft may be poor in diabetics or in the case of proximal stenosis of target right coronary <90%.