OBJECTIVES Surgical knots on the suture line provide an anchoring function, but also represent a potential source of infection and irritation on the donor leg after coronary artery bypass surgery. Knotless barbed sutures were designed to prevent knot-related complications. This study compared knot-related wound complication rates between patients receiving traditional monofilament sutures and those receiving barbed knotless sutures for closure of the donor leg. METHODS One hundred and forty-two patients were randomized into two groups. Group 1 (n = 70) received traditional monofilament sutures and Group 2 (n = 72) received barbed knotless sutures. All wounds were assessed on postoperative days 3 and 5 and weeks 2, 4 and 6 using a validated wound scoring system. Antibiotics usage and general practitioner and district nurse visits were recorded. RESULTS No demographic differences were observed between groups. Leg wound skin closure times were significantly shorter in Group 2 compared with Group 1 (P < 0.001). Group 1 demonstrated a greater incidence of excessive scarring (P < 0.001), itching (P < 0.001), irritation (P < 0.001) and adverse skin tissue reactions (P < 0.001) than Group 2. Fewer general practitioner visits were recorded in Group 1 compared with Group 2 (P = 0.051). CONCLUSION Knotless barbed suture usage significantly reduces the incidence of knot-related leg wound complications compared with traditional monofilament knotted sutures. This may be related to differences in the rate of absorption of the suture material or an associated decrease in the incidence of adverse skin tissue reactions that may delay postoperative wound healing.