In the printing plate developing process, the offset printing developer undergoes changes, as well as enrichment by the various chemicals, i.e. metals, organic binders and photosensitive compounds. The objective of this study was to investigate the electrocoagulation/flotation (ECF) treatment efficiency for the removal of copper, turbidity and organic substances from the waste offset printing developer (WOPD). The effect of operational parameters, such as electrode materials, current density, interelectrode distance and operating time, was studied. Also, the response surface analysis was applied to evaluate the effect of main operational variables and to get a balanced removal efficiency of investigated WOPD parameters by ECF treatment. The removal efficiency increases significantly with the increasing of operating time and mainly increases with the increasing of current density. The obtained results show that the interelectrode distance and combinations of electrodes determine the removal efficiency of copper, turbidity and organic substances. Based on the obtained results, the optimized parameters for the ECF treatment removal of investigated WOPD parameters were identified as: Al(−)/Fe(+) electrode combination with interelectrode distance of 1.0 cm, operating time of 5 min and current density of 8 mA cm−2. This study confirms the practical feasibility of ECF method for treating real printing industrial effluent under optimum conditions.