Nanoparticles synthesis is an sustainable and eco-friendly products using a various metal oxide. Among them, iron oxide nanoparticles come in a variety of shapes and characteristics. The Western Ghats of Karnataka is known for the cultivation of indigenous rain fed land race cultivar of Karimundaga Black rice is a edible and considered as good medicinal property. In the present study, aqueous extract of Black rice (Oryza sativa L. cultivar Karimundaga) were utilized for the synthesis of iron nanoparticles, then synthesized nanoparticles were subjected to various spectroscopic analysis such as UV-Visible spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM). Dynamic light scattering (DLS), particle size zeta potential and evaluate the antimicrobial potential against bacteria and fungus. The spectroscopic analysis results confirmed the formation of iron nanoparticles with nanoscale. The antimicrobial activity of both aqueous extract and synthesised nanoparticles showed significant zone of inhibition against bacteria namely Staphylococcus aureus & Pseudomonas aeruginosa and fungus namely Aspergillus flavus & Aspergillus Niger. The black rice showed good antimicrobial property and have good scope in further research