This study aimed to analyze the effects of light-emitting diode (LED) therapy on sternotomy pain and healing in patients who underwent coronary artery bypass grafting (CABG). The patients were followed for 6 months after the surgery to determine their dehiscence. This study was conducted with 90 volunteers who electively submitted to CABG. The volunteers were randomly allocated into three different groups of equal size: LED (λ of 640 ± 20 nm and spatial average energy fluency of 1.2 J/cm(2) during hospitalization), placebo, or control. The outcomes assessed were pain when coughing by a visual analog scale (VAS) and the McGill questionnaire and sternotomy healing by clinical assessment and photographical register end interpretation. The LED group had better pain reduction, as indicated by both the VAS and the McGill questionnaire (number of words chosen and pain index) (p ≤ 0.05), on days 6 and 8 after hospital discharge compared to the placebo and control groups. One month after surgery, almost no individual mentioned pain when coughing. Three researchers blindly analyzed the incision photographs to determine hyperemia and wound closure, and they found that the LED group had both less hyperemia and less incision bleeding or dehiscence. The LED therapy (640 nm) had an analgesic effect on the sternotomies of patients who underwent CABG, increasing their incision healing and preventing dehiscence.