The stability constants of the complex, [(C13H14N4O)2Cu]2+, which is formed by 4-4’-diaminocarbanilide and Copper (II) are determined potentiometrically for various ionic strengths by using Calvin-Bjerrum and Irving-Rossotti methods, in this work. The overall protonation constant (logβ4) is found to be 19.82 for I=0.01; 24.50 for I=0.11 and 18.74 for I=0.21. It has been found that the fourth proton of the ligand is missing when the ionic strength is high. The overall stability constant of the Copper (II) complex (logβ4) is found to be 7.55 for I=0.01; 16.05 for I=0.11 and 7.1o for I=0.21. Both the protonation constants and the stability constants first increase, then decrease together with the increase of the ionic strength. This situation can be explained by the result of various effects caused by the ionic strengths on the dissociation of species, which are derived from the ligand and which carry various charges. Keywords :