An attempt was made to deposit a nanocoating onto a cotton textile substrate using a layer-by-layer self-assembly approach. Chitosan, a natural biopolymer with polycationic characteristic, was used as a polyelectrolyte along with poly(sodium-4-styrene sulfonate) as an anionic polyelectrolyte for the first time on a textile substrate using this technique. The nanocoated surface was evaluated for surface characteristics such as the contact angle and scanning electron microscopy. The effect of ultrasonication during the intermediate washing steps was explored. Ultrasonication during the washing steps clearly helped in depositing more uniform bilayers onto individual fiber surfaces; this contrasted with the deposition of a continuous coating layer, which was nonuniform and had a lot of surface cracks. The use of this novel method for depositing chitosan onto cotton imparted antimicrobial properties to the fabric without adversely affecting its flexibility, feel, or breathability. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 2793-2799, 2011