In this work, the adsorption behaviors of chromium(III) and (VI) on the electroless Cu-plated activated carbon fibers (ACFs) have been investigated. The introduction and amount of copper on activated carbon fibers have been confirmed by atomic absorption spectroscopy. The surface properties of the ACFs studied have been characterized by using pH, acid/base values, and BET isotherm with N-2/77 K adsorption. As a result, the electroless copper plating does significantly lead to a decrease in the surface acidity or to an increase in the surface basicity in well-developed micropores of ACFs. The adsorption of Cr(III) ions is increased with the introduction of copper on ACFs, whereas the adsorption of Cr(VI) ions is decreased. The increase of Cr(III) adsorption and the decrease of Cr(VI) adsorption have been attributed to the formation of metal oxides on the ACFs studied, resulting in increasing the surface basicity. Thus, the presence of basic copper oxides on AC Fs enhances the adsorption of Cr(III) cations, as it suppresses the adsorption of Cr(VI) anions.