A magnetic composite adsorbent (Fe3O4@CuO&GO) was fabricated by combining graphene oxide (GO) sheets with Fe3O4 and CuO through coprecipitation. According to the surface characterization results, the introduction of GO not only maintained the favorable properties of the iron-copper (Fe@Cu) composite, such as the excellent magnetic characteristics and abundant hydroxyl groups, but also inhibited the aggregation of nanoscale Fe@Cu oxide particles and thus enhanced the ability of the particles to remove As(III) and As(V) from water. The kinetic data were accurately described by both a pseudo-second-order model and the Elovich model, indicating chemisorption on heterogeneous surfaces, and the Freundlich model was applicable to the equilibrium data. The maximum amounts of adsorbed As(III) and As(V) were determined to be 70.36 and 62.60 mg/g via the Langmuir model, respectively. The adsorption capacity of As(III) was minimally affected by changes in the solution pH, while the adsorption amount of As(V) decreased with the elevated solution pH. Some coexisting anions, especially phosphate, significantly influenced the As removal efficiency. Surface characterizations of the adsorbent and spectroscopic analysis results suggested that As is mainly bound to the hydroxyl groups on the adsorbent through surface complexation. Five consecutive adsorption-regeneration cycles illustrated that this adsorbent can be reused in successive As treatments. The dynamic adsorption-separation treatment of simulated As-contaminated water confirmed that this composite material can be used to remove the excess As from drinking water without causing secondary pollution and is therefore a potential material for use in engineering applications.