Unwanted activation of sphalerite and pyrite by copper ions dissolved from copper minerals (mainly chalcopyrite) hampers flotation selectivity. Galvanic interaction between the sulphide minerals is considered as the main cause for such activation. Therefore, a complexing agent, EDTA, was used to prevent unwanted activation of sphalerite and pyrite by copper ions in the presence and absence of collector. In this study, unwanted activation of sphalerite and pyrite by copper ions and inhibition of this activation by using EDTA was investigated by using cyclic voltammetry and microflotation techniques. The influence of galvanic interaction between chalcopyrite-pyrite and chalcopyrite-sphalerite on flotation selectivity and the effect of EDTA were determined with microflotation tests performed with single mineral and mineral mixtures. The results pointed out dual effect of EDTA as preventing activation of sphalerite and pyrite by copper ions, but at the same time enhancing their collectorless flotation by removing the metal hydroxides from their surfaces.