Polymer coatings featuring nonleaching antibacterial agents are needed to significantly reduce bacterial colonization and subsequent biofilm formation. Previously, single-walled carbon nanotubes (SWNTs) have been reported to be strong antimicrobial agents that kill microbes on contact. However, the antibacterial activity of freestanding polymer mats with a low weight percent of incorporated SWNTs has not been demonstrated. In this study, four different weight percents of well characterized, small diameter (0.8 nm) SWNTs were incorporated into electrospun polysulfone (PSf) mats. Electrospun PSf−SWNT mats were observed to be flexible and composed of continuous, cylindrical, and randomly oriented fibers. SEM micrographs revealed that SWNT ends were distributed along the longitudinal fiber axis. Loss of bacteria (Escherichia coli) viability was observed to directly correlate to increased SWNT incorporation within the mat, ranging from 18% for 0.1 wt % SWNTs to 76% for 1.0 wt % SWNTs. Time-dependent bacterial cytotoxicity studies indicated that the antimicrobial action of the PSf−SWNT mats occurs after a short contact time of 15 min or less. This study demonstrates the potential applicability of electrospun PSf−SWNT mats as antibacterial coatings.