Magnetite (Fe3O4) is one of the widely used materials as a catalyst in the photo‐Fenton process for the oxidation of dyes. We report about the electrochemical synthesis of the superparamagnetic Fe3O4 nanoparticles. The structure, morphology, chemical composition, and chemical state of the catalyst were characterized. The synthesized samples of superparamagnetic Fe3O4 nanoparticles were characterized using scanning electron microscopy, X‐ray diffraction spectroscopy (XRD), Raman shift spectroscopy, and vibrating magnetometer (VSM). The diffraction peaks and Raman shift spectra confirm the formation of Fe3O4. Superparamagnetic Fe3O4 nanoparticles were used as a catalyst for the oxidation of Rhodamine B (RhB) in a photo‐Fenton‐like process. The effect of operating parameters, including H2O2 concentration, catalyst concentration, and RhB concentration, on the RhB decomposition efficiency was investigated. The rate of color removal was 85 % after 12 minutes at RhB concentration of 2 mg/L, H2O2 concentration of 0.18 mM, and Fe3O4 concentration of 0.2 g/L. In addition, electrochemically synthesized superparamagnetic Fe3O4 nanoparticles showed that the catalyst activity decreased by only 7 % during recycling experiments, indicating long‐term stability of the sample.