This research is focused on application of Iron Oxide Nanoparticles (FeO on bacterial pathogens of tomato wilt. Ralstoniasolanacaerumis the major bacterial pathogen causing tomato wilt. FeO NPs are synthesized by co-precipitation technique and calcinated to reduce size and impurities of NPs. After synthesis, their zeta potential is analyzed which showed negative surface charge predicting efficacy against gram negative organisms. Their physiochemical characterization is done through Scanning Electron Microscope (SEM), (X-Ray Diffraction Analysis (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Characterization reveals that their size in 16-67nm diameter and the FeO NPs are non-uniform in size. 43 tomato plants showing typical wilt symptoms are collected from field and their exudates from stem and crushed leaves are cultured on nutrient media. 17 samples are positive for bacterial growth. Bacterial positive samples are sub-cultured on TTZ selective media for Ralstoniasolanacaerum. Bacterial samples are confirmed by gram staining, biochemical testing i.e. catalase and oxidase positive. Identified Ralstoniasolanacaerum is spread on nutrient petri plate and four concentrations of FeO NPs i.e. 25, 50, 100 and 200µg/ml are applied to check zone of inhibition by disc diffusion method along with positive and negative controls. At 200µg/ml conc. Of FeO NPs zone of inhibition is average 11mm diameter as compared to positive control 14mm diamteter, and this is quite significant. FeO NPs showed significant antibacterial effects against Gram Negative Ralstonia solanacearum responsible for bacterial tomato wilt.