Antibacterial thermoplastic polyurethane (TPU) electrospun fiber mats were prepared by adsorption of Ag nanoparticles (Ag NPs) onto TPU/3-aminopropyltriethoxysilane (APS) co-electrospun fiber mats from silver sol. The use of APS can functionalize TPU fibers with amino groups, facilitating the adsorption of Ag NPs. The effects of pH of silver sol and APS content on Ag NP adsorption and antibacterial activity were investigated. Ag NP adsorption was evidenced by TEM, XPS and TGA. Significant Ag NP adsorption occurred at pH = 3-5. The main driving force for Ag NP adsorption is electrostatic interaction between aEuro center dot NH3 (+) of the fibers and aEuro center dot COO- derived from the aEuro center dot COOH group capped on the surfaces of Ag NPs. The antibacterial activity of the Ag NP-decorated TPU/APS fiber mats was investigated using both gram-negative Escherichia coli and gram-positive Bacillus subtilis. The antibacterial rate increases with increasing APS content up to 5% where the antibacterial rates against both types of bacteria are over 99.9%.