To enhance As(V) removal, an activated carbon fiber (ACF) based adsorbent was fabricated by impregnation of nano-sized magnetite to the surface of ACF with chitosan as the coating support. The As(V) adsorption capacity of the modified ACF (MACF) was approximately eight times of that of the raw ACF (RACF). Even at As(V) concentrations lower than 10 μg L-1, the MACF exhibited a considerably high adsorption capacity to As(V), whereas the RACF was ineffective even at an As(V) concentration ten times higher to 10 μg L-1. The MACF was able to reduce As(V) concentration below its maximum contaminant level regulated by the US EPA for drinking water in a wide pH range without formation of the more poisonous As(III). Kinetic experiments indicated that the diffusion of As(V) within the pores of the MACF was more rapid than that of the RACF and that the surface reaction was the dominant step in the adsorption of As(V) onto the MACF. Compared with the RACF, the MACF had a wider applicable pH range from 2 to 8 for the As(V) uptake. Besides enhanced As(V) uptake, the MACF maintained its high adsorption capability to organic contaminants, such as phenol and humic acid.