A 3D-printed prototype of an electrochemical flow cell for the synthesis of superparamagnetic magnetite nanoparticles of medium size between 15 and 30 nm was constructed and its performance was evaluated. The cell consists of a series of rectangular channels in a parallel electrode arrangement. Electrolyte flows through the channels as the electric current is supplied to the system and a combination of electrochemical and chemical reactions create the appropriate conditions for magnetite precipitation. Different electric configurations were evaluated and both energy and production efficiencies were calculated to determine the best configuration. Different flow and current values were also investigated, and all the materials were analyzed by X-ray diffraction, transmission electron microscopy, Mossbauer spectroscopy and magnetization curve measurements to determine their effect on particle morphology, composition and magnetic behavior. The best results were obtained for a parallel monopolar configuration, with 100 mA (3 mA cm(-2)) passing in each two electrodes and a flow value of 30 mL min(-1), yielding an energy efficiency of 5.9 kJ g(-1) and a production rate of 12.1 mg min(-1), approximately 6 times higher than the 100 mL standard cell previously used. Magnetic saturation was 77.3 emu g(-1), slightly lower than the bulk material (92-100 emu g(-1)). (C) 2018 The Electrochemical Society.