Blue light has seen very promising effects on wound healing in recent clinical studies, with the underlying principle of photobiomodulation as the key mechanism. As a minimally invasive, well-tolerated adjunct to treatment for wounds, blue light therapy would be extremely attractive and simple to implement. The underlying physiological basis revolves around receptive molecules dubbed chromophores that absorb light energy and trigger a physiological response. For blue light, this typically occurs in the mitochondria of cells, where formation of reactive oxygen species (ROS), among other messenger molecules, results in a cascade of signaling that ultimately result in angiogenesis, improved granulation, and re-epithelialization of wounds. ROS have been identified as the critical first molecules that are formed post-illumination, and most of the benefits from blue light stem from the increased local production of ROS. The effect is particularly profound in chronic wounds that have stagnated and are not progressing along the wound healing pathway. This stagnation occurs during the inflammation phase of wound healing; thus, there is a need to trigger progression into the proliferation phase to result in wound healing. Another contributing factor is the antimicrobial property of blue light, with inhibitory, even bactericidal effects on most common infective organisms involved in wounds through infection or biofilm formation, both of which are known to inhibit wound healing. There is strong evidence that the underlying in vitro findings of these effects are carried out in vivo, and there is emerging clinical evidence that there is a significant difference in wound healing promotion that blue light elicits. This chapter explores the steps through which blue light application onto a wound is able to promote wound healing via key chromophores and the resultant effect.