In the present work, 1-ethyl-3-methyl imidazolium chloride C3MIMCl combine with ultra-soni-cation was applied for extraction of bioactive compounds from Polygonum minus. The extract was used to synthesize nickel nanoparticles (Ni NPs). Synthesis was confirmed by UV/Vis spectropho-tometry. The Ni NPs were characterized by X-ray diffraction (XRD), Fourier Transformed Infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The morphology was identified by Field Emission Scanning Electron Microscopy (FESEM) and the particle size and zeta potential were analyzed by dynamic light scattering (DLS). Nickel nanoparticles were used for degradation of methyl red, methyl orange, methylene blue and degraded 98% of all dyes in time interval of 5, 5 and 10 min respectively. The synthesized nickel nanoparticles were found to be highly effective against three different bacteria such as Aeromonas hydrophila (AH), Escherichia coli (EC), Staphylococcus aureus (SA) in disc diffusion methods at various concentrations. © 2018 Desalination Publications. All rights reserved.