The modified ISEs sensors show high selectivity and sensitivity for determination of copper(II) and iron(III) ions over the other ions. Also they showed stable and reproducible response over a period of five and three months for Copper(II) SPE and CPE sensors, respectively, and 86, 74, 66 and 95 days for Fe(III) electrodes (I, II, III and IV), respectively. This method can be used for potentiometric determination of copper (II) and iron(III) in water, soil, plant and fish tissue samples and the obtained results agreed with those obtained with atomic absorption spectrometer (AAS). Cu(II)-SPEs, CPEs and Fe(III)-CPEs showed advantages over other methods as high performance, selectivity, sensitivity in a wide range of activities, long-term stability, wide pH range, fast and easy preparation procedures, simple instrumentation, low cost and higher calibration graph slopes.