A new chemically modified carbon paste electrode (CMCPE) based on etioporphyrin I has been developed for the determination of Cu2+ in real samples. The performance of this electrode was investigated using potentiometric measurements. The developed sensor exhibits a good linear response with a slope of 30.30 mV per decade over the concentration range of 1.28 x 10(-6)-1.28 x 10(-2) mol L-1. It has a very low limit of detection, 8.99 x 10(-7) mol L-1, with response time of 5 s. The proposed electrode revealed very good selectivities with respect to alkali, alkaline earth and some transition metal ions and could be used in pH range of 4.5-8.5. The thermal stability of the electrode was studied. This modified electrode was successfully applied as an indicator electrode for potentiometric titration of Cu2+ with EDTA and CDTA. Also the electrode was applied for direct determination of copper in different water samples, milk powder, brass powder and copper rod. (C) 2011 Elsevier By. All rights reserved.