The electrochemical behaviour of Cu(II) ions has been investigated in acidic aqueous solutions in the presence of dicyanamide (dca), an anion frequently used as bridging agent in coordination polymers. The cyclic voltammograms recorded at a gold electrode have revealed two consecutive one electron transfer processes indicating that Cu(I) is stabilized by the dicyanamide anion at the electrode surface. The formation of an insoluble film after reduction of Cu(II) to Cu(I) was evidenced by EQCM measurements and imaged by scanning electron microscopy. XRD and infrared reflection spectroscopy data have confirmed the formation of a Cu(I)-dca film.