Silver nanoparticles were deposited on the surface of natural wool with the aid of powered ultrasound. The average particle size was 5-10 nm, but larger aggregates of 50-100 nm were also observed. The sonochemical irradiation of a slurry containing wool fibers, silver nitrate, and ammonia in an aqueous medium for 120 min under an argon atmosphere yielded a silver-wool nanocomposite. By varying the gas and reaction conditions, we could achieve control over the deposition of the metallic silver particles on the surface of the wool fibers. The resulting silver-deposited wool samples were characterized with X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, high-resolution scanning electron microscopy, electron-dispersive X-ray analysis, Brunauer, Emmett, and Teller physical adsorption method, X-ray photoelectron spectroscopy, and Raman and diffused reflection optical spectroscopy. The results showed that the strong adhesion of the silver to the wool was a result of the adsorption and interaction of silver with sulfur moieties related to the cysteine group.