In this work, a ferromagnetic graphene oxide nanocomposite (mGO) was produced, characterized, and tested for clonazepam removal from water. After the nanocomposite production and characterization, adsorption tests showed that the initial pH does not influence the clonazepam removal. Clonazepam adsorption onto mGO was an extremely fast process, with equilibrium reached within the first minutes. Sips isotherm showed the best fit to the experimental data, presenting a maximum adsorption capacity of 14.81 mg g−1, indicating that the clonazepam adsorption process is favorable. Pseudo-first order was the empirical kinetic model that best fit the experimental data, with R2 > 0.99; as for the phenomenological models, both the Linear and Quadratic Driving Force models fit the data with R2 > 0.97. Moreover, the regenerative and reuse potential of the nanocomposite was analyzed, exhibiting remarkable regeneration potential, even after 5 adsorption/desorption cycles. Finally, according to the phytotoxicity tests, it was observed that the effluent treated with mGO did not present toxicity to watercress seeds, as all seeds germinated. This work stands out because it proposes a nanoparticle composite material for the viable, efficient, eco-friendly, and easy removal of an emerging contaminant from water.