Cu smelter slag contains more than 40 wt% Fe, mostly in fayalite (Fe2SiO4) phase, as well as oxides of non-ferrous metals such as Cu, Co, Ni, and Zn. In this study, the recovery of Fe from the Cu smelter slag via an electrochemical process in HNO3-based solutions is investigated as an aspect of impurity control by varying both the applied cathodic potential and bath chemistry. The Cu smelter slag was preliminarily reduced to Fe alloy including 1.04 wt% Cu and 0.46 wt% Si via the melting reduction method. The Fe alloy was completely dissolved in a concentrated HNO3 solution for electrochemical reduction of Fe at constant cathodic potentials. NaOH and NH4Cl were added to control the solution pH and suppress the precipitation of alpha-FeO(OH), respectively. Cu and Si within the produced Fe deposit were at non-detectable levels. The lowest O/Fe weight ratio in the Fe deposit was 0.011 by adding 0.561 M NH4Cl to the HNO3-based solution, indicating that 1.09 wt% oxygen was contained.