In the present work, a reduced graphene oxide and multiwalled carbon nanotube (RGO/MWCNTFe₃O₄) composite decorated with Fe₃O₄ magnetic nanoparticles was prepared as an electrochemical sensor. The surface morphology of the prepared composite was identified by scanning electron microscopy and X-ray diffraction. The electrochemical properties of the GCE/RGO/MWCNT-Fe₃O₄ electrode were investigated by electrochemical impedance spectroscopy, cyclic voltammetry and amperometry. The GCE/RGO/MWCNT-Fe₃O₄ electrode exhibited higher electrocatalytic performance towards the oxidation of hydrazine. In the optimal conditions, the GCE/RGO/MWCNT-Fe₃O₄ electrode showed a wide linear range (0.15-220 μM), low limit of detection (LOD) (0.75 μM), and high sensitivity (2.868 μA μM-1 cm-2). The prepared GCE/RGO/MWCNT-Fe₃O₄ electrode also had excellent repeatability, selectivity, and reproducibility. The practical application of the electrode was confirmed with various spiked water samples and demonstrated acceptable recovery.