In this study, vapor phase deposition of quaternary ammonium polymers on different substrates was reported. Thin films of the poly(diethylaminoethyl methacrylate) (PDEAEMA) homopolymer and the poly(diethyl aminoethyl methacrylate-co-vinylbenzyl chloride) [P(DEAEMA-VBC)] copolymer were deposited by an initiated chemical vapor deposition (iCVD) technique using tert-butyl peroxide as an initiator. The variation of monomer feed ratios allowed control over the film structure. In the film structure, the tertiary amine group of DEAEMA is a key functionality behind the antibacterial activity, as verified after Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses. The PDEAEMA homopolymer could be quaternized in a dry manner using an oxygen plasma treatment. The P(DEAEMA-VBC) copolymer, however, did not need an extra quaternization step because the tertiary amine group of the polymer could be readily quaternized by the chlorine moiety of the VBC unit. Both the homo- and copolymers exhibited high antibacterial activity on three different substrates, namely, glass, a polyethylene terephthalate sheet, and fabric. The antibacterial activity depended on the intensity of the quaternized nitrogen atoms in the as-deposited polymer. The adhesion and durability of the copolymer films were superior to that of the homopolymer film, verified using an adhesive tape peel-off test. The most durable copolymer film exhibited very high log-reduction values (>3) against gram-negative and gram-positive bacteria. Based on e cell viability analysis, the antibacterial films deposited by iCVD in this study were found to be nontoxic.