Silver nanoprisms are used as antimicrobial agents for medical applications due to their large surface area, which provides better contact with microorganisms. However, silver nanoprisms are toxic to mammalian cells. To alleviate this problem, synthesis of silver nanoprisms via a light-induced transformation reaction with LED light was proposed. This reaction was ecofriendly and excluded hazards from the use of harmful oxidizing agents. Different shape and size of the as-grown silver nanocrystals could be distinguished by their colors. Results showed that the nano-octahedron photomediated silver nanoprisms showed the strongest bacterial inhibition with MIC and MBC value of 6.74, 6.74, 13.38, and 6.74 μg/mL against Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, and methicillin-resistant Staphylococcus aureus (MRSA), respectively. Silver nanoprisms were later impregnated within bacterial celluloses (BC) and the resulting composite films (PAgNPrs/BC) also exhibited the antibacterial activity against the four above microbes. Indirect cytotoxicity evaluation of the PAgNPrs/BC-composite films with human dermal fibroblasts proved that these films were non-toxic. All the results suggested that the PAgNPrs/BC-composite films could be used to care for certain infectious wounds.