In this work, poly(acrylic acid) has been grafted onto cotton fibers through the free radical initiated polymerization and the resulting fibers have been characterized by Fourier transform infrared, thermogravimetric analysis, and scanning electron microscopy analysis. The grafted fibers have been loaded with copper nanoparticles using in situ approach. The Transmission Electron Microscopy (TEM) analysis of Cu nanoparticles revealed that almost 45% of the particles had a diameter range of 60–80 nm. The copper nanoparticles loaded fibers show slow release of Cu(II) ions, extended over a period of around 50 h. The release of Cu(II) ions followed a second-order kinetic model successfully. The fibers also exhibited an excellent antibacterial action against model bacteria Escherichia coli as tested by zone of inhibition method.