The effect of a new additive (IT-85) representing a mixture of triethyl-benzyl-ammonium chloride (TEBA) and hydroxyethylated-2-butyne-l,4-diol (‘Ferasine’) on the kinetics of copper electrodeposition from sulphate acidic electrolytes, as well as on the morphology and structure of copper deposits was investigated and compared with those exerted by its two components, TEBA and Ferasine. Quasi-steady state hydrodynamic voltammetry at a rotating-disc electrode and electrochemical impedance spectroscopy were performed in order to obtain information about the kinetics of the cathodic process. SEM and X-ray diffraction analysis were used to examine the morphology and the structure of copper deposits. The kinetic parameters (αc, k0) obtained by both Tafel and Koutecky-Levich interpretations showed that all tested organic additives have an inhibiting effect on copper electrodeposition. Unlike IT-85 or Ferasine, TEBA acts only as a blocking agent in the copper discharge process, without changing the reaction pathway corresponding to the absence of additives. Comparison of the inhibiting effects exerted by IT-85 and its components on the electrodeposition process pointed to the existence of a beneficial complementarity of TEBA and Ferasine when they are used in mixture.