Fabrication of antibacterial surfaces is an approach to reduce environmental bacterial burden and risk of infection transmission. Antibacterial coatings based on cationic polymers have been commonly used for this purpose, but coating methods to immobilize these polymers over large area substrates are limited. Herein, we report a facile aqueous-based method of immobilizing quaternized chitosan (QCS) on polymer and metal substrates via electrostatic interaction with substrate-anchored multivalent polyphosphate ions to form transparent antibacterial coatings of micron thickness. The QCS coatings are noncytotoxic and yet demonstrate a high killing efficacy against two clinically relevant bacteria, Staphylococcus aureus and Pseudomonas aeruginosa, when challenged with bacteria-loaded droplets or contacted with a bacteria-loaded dry surface. The coatings were stable when subjected to wiping, and the QCS-coated substrates retained their efficacy and could be reused for multiple cycles after wiping the contaminated surface with 70% ethanol. A distinct advantage of this coating method is the ease of scale-up using spray coating for preparation of uniform large area coatings.