Microwave sintered magnesium ferrite (MF) nanoparticles are synthesised by hydrothermal technique. X-ray diffraction revealed pure spinel phase but low crystallinity. Synthesised MF is observed to be in nanoscale under scanning electron and transmission electron microscopes. MF is characterised further by Fourier transform infrared and UV-visible spectrometers for vibrational bands and optical band gap information. Electric and magnetic characterizations revealed low conductivity, dielectric loss, magnetic loss and fairly good initial permeability. High coercivity and M-H loop area of MF indicate the hard magnetic nature. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.