A novel electrochemical sensor was fabricated by electrodeposition of silver nanoparticles on pre-synthesized polypyrrole (PPy), to form a PPy/Ag composite matrix on a glassy carbon electrode. The electrochemical sensor exhibited strong catalytic activity with regards to nitrate reduction. Scanning electron microscopy and cyclic voltammetry were used for the characterization of the composite. The detection limit of nitrate was found to be 5 mu M. Moreover, the sensor showed excellent sensitivity, selectivity, and stability.