Open-cell silver foams with various pore sizes (494, 337, 126 and 39 μm) and porosity (60, 70 and 80 vol%) were produced using a powder-based replication method. It was found that the foams have strong microbial reduction efficiency. The antimicrobial effect of the foams is much stronger on gram-negative bacterium (Escherichia coli) than gram-positive bacterium (Staphylococcus aureus). With equivalent volume addition of NaCl particles, higher antimicrobial effect was found for Ag foams with larger pore size. The difference on antimicrobial effect between silver foams with various pore sizes is smaller when porosity of the foams increases from 60 to 80%. No correlation between particle sizes of NaCl and bacterial growth inhibition was found. In addition, effect of particle sizes and pore sizes of the foams on the bacterial growth inhibition is not as much as the effect of particle addition. It is expected that the positively charged Ag ions released from the surface of Ag foam structure would alter the morphology of bacteria strains in which disruption of cell wall and eventually damage were implemented.