Purpose Pectoralis major tendon avulsion injury benefits from surgical repair. The technique used and speed of rehabilitation in this demanding population remains subject to debate. We performed a biomechanical study comparing suture button (Pec Button™, Arthrex, Naples, FL) with a transosseous suture technique (FibreWire, Arthrex, Naples, FL). Methods Freshly slaughtered porcine humeri were prepared to model a single transosseous suture or suture button repair. A static, tensile load to failure experiment and a cyclic, tensile load experiment to model standard (10,000 cycles) and accelerated rehabilitation (20,000 cycles) philosophies were tested. The mode of failure, yield and ultimate failure load, extension (clinical failure >10 mm) and the resistance to cyclic loading was measured. Results The mode of failure was suture fracture in all the static load experiments with 10/11 occurring as the suture passed through the button and 7/11 as the suture passed through the bone tunnels. There was a significant difference in yield load, favouring transosseous suture [p = 0.009, suture button (SB) 673.0 N (647.2-691.7 N), transosseous suture (TOS) 855.0 N (750.0-891.4 N)] and median extension, favouring suture button [p = 0.009, SB 8.8 mm (5.0-12.4 mm), TOS 15.2 mm (13.2-17.1 mm)]. 2/3 transosseous suture and 0/3 suture buttons failed before completing 20,000 cycles. The difference in mean number of cycles completed was non-significant. The difference in mean extension was 5.1 mm (SB 6.7 mm, TOS 11.7 mm). Conclusions Both techniques show advantages. The difference in extension is likely to be more clinically relevant than load tolerated at failure, which is well above physiological levels. The findings do not support an accelerated rehabilitation model.