In this study, ZnFe 2 O 4 magnetic nanoparticles were used to modify a screen printed electrode. The modified electrode decreased the over-potential of vitamin C (70 mV) and prominently increased its oxidation peak current (3.3%). Under optimum conditions, the electrode provided a linear response based on the vitamin C concentrations between 0.5-500.0 μM, with a detection limit of 0.15 μM, by using the differential pulse voltammetric method. The modified electrode exhibited excellent electrochemical performance, including a good linear range and a micromolar detection limit, high sensitivity, and desirable stability and repeatability. Particularly, the practical applicability was revealed by quantifying the vitamin C concentrations in real samples.