Tissue adhesion after surgery occasionally causes serious complications. The authors have been developing photocurable mucopolysaccharides for a tissue adhesion prevention material that meets requirements such as nonadherent surface characteristics, biocompatibility, biodegradability in accordance with the wound healing rate, and nontoxicity. Mucopolysaccharides (hyaluronic acid and chondroitin sulfate) partially derived with photoreactive groups, such as cinnamate or thymine, were subjected to ultraviolet (UV) irradiation to produce water insoluble gels via intermolecular photodimerization of photoreactive groups. Photocured films that covered injured liver surfaces of rats were implanted for as long as 4 weeks and histologically evaluated. In vivo performance, including tissue adhesion prevention, biodegradability, and mechanical flexibility of the films, was found to be controlled by the type of mucopolysaccharides, the type of photoreactive groups, and their degrees of substitution (DS). Photocured films with lower DS, which had high water swellability and flexibility, prevented tissue adhesion and exhibited enhanced biodegradability. As an increase in DS occurred, tissue adhesion prevention, biodegradability, and mechanical flexibility were reduced. Control of the biodegradation rate was feasible. Minimum inflammatory reaction was noticed.