Nanohybrids of nylon 6 and nano-titania ($TiO_2$) were prepared by melt compounding with a twin-screw extruder to investigate antibacterial activity. It was confirmed by field emission scanning electron microscopy (FESEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD) that nano-$TiO_2$ was successfully dispersed in the nylon 6 matrix at the level of individual particles. After immersion in an aqueous solution of $AgNO_3$ at 100 ppm Ag ion concentration, silver was introduced to the nanohybrids through photocatalytic reduction by nano-$TiO_2$ under UV (254 nm) irradiation. With increasing nano-$TiO_2$ content, the nanohybrids with silver photodeposited on the nano-$TiO_2$. The nylon $6/TiO_2$-Ag nanohybrids exhibited strong antimicrobial activity against Klebsiella pneumoniae and Staphylococcus aureus in measurements with the shaking flask method.