The global demand for sustainable and functional fibers and textile materials is increasing with the pressure to limit the synthetic petroleum-based counterparts. In this study, we use ultrasonication for the preparation of eco-friendly cellulose fabrics bearing silver or gold nanoparticles (NPs). The mechanochemistry of cellulose is based on the breakage of glycosidic bonds and the formation of mechanoradicals. These mechanoradicals can reduce Au3+ and Ag+ ions in solution, and the reduced metals can be stabilized by the cellulose chains as nanoparticles. Here, we formed the mechanoradicals in the fabrics by sonication (on the order of 1018 per gram), which is confirmed by ESR. The sizes and the metallic nature of NPs and the structural and morphological changes in the fabrics upon ultrasonication were studied by SEM, XPS, FTIR-ATR, XRD, and TEM. The displayed preparation method is shown to yield antibacterial AgNP-fabric and catalytically active AuNP-fabric composites, with up to a 14% yield of metal ion reduction. Since the method involves only the sonication of the fabric in aqueous solutions, and uses no hazardous reducing and stabilizing agents, it provides quick and environment-friendly access to fabric nanocomposites, which have applications in medical textiles, catalysis, and materials for energy.