Existence of silver ion in wide range of applications have led to a considerable increase of its concentration in environment. As a consequence and due to probable environmental and health issues, development of a highly sensitive and reliable method for the determination of Ag ion in environmental samples such as water is essential. An ion-selective potentiometric sensor was developed by introducing graphitic carbon nitride (g-C3N4) as a novel ion career to detect the trace level of silver ion in water samples. The graphitic carbon nitride (g-C3N4) nanosheets were synthesized and then characterized by scanning electron microscopy, Uv-vis spectroscopy, fluorescence spectroscopy, XRD and FT-IR. The material was synthesized and then used for the modification of a carbon paste electrode. The electrode containing 14.3% n-eicosane, 80.7% graphite powder and 5.0% g-C3N4, presented the stable potential response to Ag+ ion with the Nernstian slope of 54.2 mVdecade(-1) at 25 degrees C. The proposed sensor exhibited reliable response over a wide linear concentration range of 1.0 x 10(-6)-1.0 x 10(-1) mol L-1 with a detection limit of 9.0 x 10(-7). The sensor provided no memory effect, prompt response time and long-term stability. The implemented electrode was resistant against interfering foreign ions such as Hg2+, Cd2+, Cu2+, Pb2+ and Cr3+.