Two oxidized carbon fibers (o-CF and o-CF-400) with microporous structure and surface area as high as ~ 1500-1130 m2/g were prepared from commercial carbon fiber felt to be used as good carbon adsorbents for removing highly toxic organic pollutant. The obtained oxidized CF samples were characterized by SEM, N2 adsorption isotherms at -196oC as well as Boehm's titration and FTIR techniques. Removal of p-nitrophenol (p-NP), as a probe organic pollutant existed in wastewater of various industries, was studied in a batch mode. Kinetic and equilibrium adsorption studies were investigated and found that the adsorption data of p-NP molecules were well-fitted with pseudo-second-order model and Langmuir isotherm. Based on the porosity developed in oxidized CFs, PNP molecules are mostly accommodated onto micropores. An oxidized carbon fiber, o-CF showed the higher removal of p-NP than that obtained using o-CF-400 due to its high micropore surface area (1450 m2/g). It was clearly observed that the adsorption of p-NP depended remarkably on the surface area of carbon fibers. It was found that values of monolayer adsorption capacity obtained by application of Langmuir equation were 258 and 155 mg/g using o-CF and o-CF-400 adsorbents, respectively, at 25oC and pH 4. Finally, it can be concluded that the both oxidized carbon fibers can be emerged as effective adsorbents because they exhibited a great adsorption capability in removing organic pollutants from wastewater.