This research work reported a highly selective and stable chloramphenicol sensor based on cyclic voltammetry. The sensor was fabricated using graphene-iron oxide nanoparticles modified on a magnetic screen-printed electrode (MSPE). The nanocomposite has remarkable enhancement in large surface areas, facilitates electron transfer to electrode surfaces, and possesses superparamagnetism property. The electrochemical properties were characterized by cyclic voltammetry (CV). The modified electrode provided a fast electron transfer with an apparent electron transfer rate constant (ks) of 0.88 s −1 . The proposed biosensor showed fast CV response (3 s) to chloramphenicol with a wide linear range from 0.05 to 0.5 mM, a low detection limit of 17 μM at a signal to noise ratio of 3 (S/N=3), and good sensitivity (22.788 μA/μM). The resulted biosensor also showed high stability and good reproducibility.