The global concern over water pollution caused by contaminants of emerging concern has been the subject of several studies due to the complexity of treatment. Here, the synthesis of a graphene oxide-based magnetic material (GO@Fe₃O₄) produced according to a modified Hummers’ method followed by a hydrothermal reaction was proposed; then, its application as a photocatalyst in clonazepam photo-Fenton degradation was investigated. Several characterization analyses were performed to analyze the structure, functionalization and magnetic properties of the composite. A 2³ factorial design was used for the optimization procedure to investigate the effect of [H₂O₂], GO@Fe₃O₄ dose and pH on clonazepam degradation. Adsorption experiments demonstrated that GO@Fe₃O₄ could not adsorb clonazepam. Photo-Fenton kinetics showed that total degradation of clonazepam was achieved within 5 min, and the experimental data were better fitted to the PFO model. A comparative study of clonazepam degradation by different processes highlighted that the heterogeneous photo-Fenton process was more efficient than homogeneous processes. The radical scavenging test showed that $${O}_{2}^{\cdot -}$$O 2 · - was the main active free radical in the degradation reaction, followed by hydroxyl radicals (^•OH) and holes (h⁺) in the valence layer; accordingly, a mechanism of degradation was proposed to describe the process.