In this work, a new anion exchanger adsorbent was synthesized based on modified natural polymeric fish bone powder. The obtained adsorbent was investigated by Field Emission Scanning Electron Micrographs (FESEM), Thermo Gravimetric Analysis (TGA), and Fourier transform infrared (FT-IR) spectra. The effects of solution pH, contact time, initial concentration of nitrate, adsorbent dosage, temperature, and competing anions (ammonium chloride, phosphate, bicarbonate sodium, magnesium sulfate) on nitrate adsorption were investigated. The maximum nitrate removal efficiency was achieved 98.83%. Antimicrobial activity of adsorbent was carried out by disc diffusion method against two Gram-negative bacteria namely E. coli and P. aeruginosa, and also two fungi species of Aspergillus niger and Saccharomyces cerevisiae in vitro.