In this study, antibacterial activity of the prepared nanocomposites [poly (o-methoxy-aniline); POMA] at different concentrations was tested on bacterial strains. Nanocomposites were prepared by in situ chemical polymerization of ortho anisidine monomer in acidic medium with ammonium peroxydisulphate (APS) as an oxidant. The composition, structure and morphology of the polymer and nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD) and ultraviolet-visible (UV-vis) spectroscopy. Different concentrations of nickel nanoparticles (1%, 2%, 3%, 4%, 5%) were used to confirm the characteristics of the synthesized nanocomposites. Antibacterial activity was tested against two strains: E. coli and S. typhi. A significant increase in the antibacterial activity of nanocomposites has been observed with an increase in concentration of nickel nanoparticles (Ni NPs). Excellent antibacterial activity was observed with nanocomposite having 5% Ni NPs.