Poly(vinylpyrrolidone)-iodine (PVP-I) is a potent antiseptic widely employed for wound cleansing, tool sterilization, and water purification, and silver ions (Ag(I)) are a well-known antimicrobial material. Although the bactericidal effects of each individual species have been well established, the synergistic potential between PVP-I and Ag(I) remains insufficiently proven. This study investigates the synergistic antibacterial effect of the combined PVP-I/Ag(I) system. In the co-presence of Ag(I) and PVP-I, the inactivation efficacy of the system was significantly improved against two gram-negative bacterial species, Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), and two gram-positive bacterial species, Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtilis). This enhancement could primarily be attributed to the heightened production of highly oxidizing hypoiodous acid (HOI). The equilibrium among reactive iodine species (e.g., iodine (I₂), triiodide ion (I₃^-) and HOI) in the PVP-I solution is profoundly influenced by the presence of iodide ions: the higher iodide ion concentration results in a low HOI concentration. However, in the presence of Ag(I), Ag(I) reacts with iodide ions to form insoluble silver iodide precipitates, thereby altering the equilibrium in favor of HOI production. The formation of such precipitation was confirmed through UV-Vis absorption spectra analysis. Furthermore, the HOI concentration in the PVP-I/Ag(I) system was found to be approximately two times higher than that of the PVP-I system, which was consistent with the theoretical calculation results.