Magnesium nitrate and sodium hydroxide are used as a starting material for the preparation of nanoparticles of magnesium oxide (MgO) via the sol–gel technique. The synthesized nanopowder of MgO was characterized by analytical technique such as the X-ray diffraction technique (XRD). The XRD analysis shows that nanocrystalline size of MgO remarkably with the 1:1 molar ratio. The respective average crystalline size is found to be 25.91 nm. The resistance of MgO nanoparticles is temperature dependent and decreases exponentially (from 1011 Ω to 107 Ω). The activation energy of the MgO nanoparticles is found to be 0.49 eV or 48.196 kJ/mol by using Arrhenius plot. The I/V characteristics of MgO nanoparticles are found to be linear in nature and obey the Ohms law in the operating temperature range (50–350 °C).