Amberlite XAD-4 polymeric resin was chemically modified with an acetyl group, which enables the resin to be used directly without a wetting process. The modified resin was comparatively evaluated using four phenolic compounds, phenol, p-cresol, p-chlorophenol, and p-nitrophenol. The capacities of equilibrium adsorption for all four phenolic compounds from their aqueous solutions increased around 20% on the acetylated resins within temperature range of 283-323 K. Freundlich isotherm equations, as well as the relative adsorptive capacities and isosteric adsorption enthalpies for the four phenolic compounds, indicate a physical and multiple-layer adsorption process on the Amberlite XAD-4 resins either with or without the chemical modification. Mini-column adsorption studies showed that the breakthrough adsorption capacity and the total adsorption capacity at designated conditions for all four phenolic compounds also increased over 20% after chemical modification.