The results of the magnetic fields effect on the heat transfer characteristics and pressure drop in a confined single jet impingement of mini-rectangular heat sink have been presented. The test section (heat sink) is fabricated from the brass block by the wire electrical discharge machine with the length * width and the fin height of 50 * 50 mm and 2 mm, respectively. The nanofluids mixture of de-ionized water and nanoscale TiO2 particles with various concentrations of 0.005%, 0.010%, 0.015% by volume are used as working fluid. Two different magnetic fields strength of 0.084, 0.28 mu T are generated by the Neodynium permanent magnetic bars. It is found that with the magnetic field effect, the Nusselt number tends to increase, compared to that without magnetic field effect, and the Nusselt number also increases with increasing the magnetic field strength. Due to the thin nanofluids concentration in this study, however, the nanofluids concentration has no significant effect on the pressure drop across the test section. (C) 2017 Elsevier Ltd. All rights reserved.