Photochemistry is the study of photochemical reactions between light and molecules. Recently, there have been increasing interests in using photochemical reactions in the fields of biomaterials and tissue engineering. This work revisits the components and mechanisms of photochemistry and reviews biomedical applications of photochemistry in various disciplines, including oncology, molecular biology, and biosurgery, with particular emphasis on tissue engineering. Finally, potential toxicities and research opportunities in this field are discussed.