The synthesis of metal oxide nanoparticles with the use of fruit waste is a promising alternative to traditional chemical methods. Generally various synthesis techniques are available to prepare MgO nanoparticles. Present work focus on synthesis of magnesium oxide nanoparticles by orange fruit waste from green method. It acts as reducing agent for synthesis of MgO because orange fruit contain Citric acid, as main source in its peel. This method is non-toxic and eco-friendly. The biologically synthesized MgO nanoparticles were characterized by UV-Visible spectroscopy to analyse the absorption patterns, Fourier transform infrared spectroscopy (FTIR) is used for analysing the functional groups and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for morphological studies. MgO nanoparticles also exhibit very good antimicrobial and antibacterial properties.