A simple method was employed to prepare stable, magnetic graphene oxide, with few layers (MGO), by loading graphene oxide (GO) onto Fe₃O₄ nanoparticles. Magnetic chemically reduced graphene (MCRG) and magnetic annealing reduced graphene (MARG) were prepared from the reduction of MGO with hydrazine hydrate and thermal reduction at 500 °C, respectively. The adsorption of Cd(II) and As(V) by MGO, MCRG and MARG were investigated to determine their adsorption properties and molecular mechanisms. The adsorption of Cd(II) and As(V) was pH-dependent and their adsorption capacities followed the order: MGO > MCRG > MARG. Therefore, MGO was selected to systematically study their adsorption behavior in the binary system of Cd(II) and As(V). The maximum adsorption capacities of MGO were 234 mg/g for Cd(II) and 14 mg/g for As(V). The superiority of MGO was mainly attributed to its high dispersibility, thin nanosheets and various O-containing functional groups. The adsorption of Cd(II) and As(V) in the co-adsorption system was increased by 65% and 30%, respectively. This synergistic effect resulted from electrostatic attraction and the formation of type A ternary surface complexes.These new results are valuable for determining the interaction mechanisms, and for designing novel adsorbents, for traditional and emerging pollutants in the environment.