The investigation is concerned with the drop of current efficiency (CE) of copper deposition under pulsed current conditions. A mathematical model which is based on different charge transfer rates between the following two reactions, $$Cu^{2 + } + e \to Cu^ + $$ (1) and $$Cu^ + + e \to Cu$$ (2) has been formulated to describe the behaviour of a Cu/CuSO4 system under pulsed current conditions on a rotating disc electrode. The results indicate that the CE drops continuously as the difference between the exchange current densities of the two reactions increases. The exchange current densities of Reactions 1 and 2 were estimated to be 0.034 mA cm−2 and 0.024 mA cm−2, respectively. Prediction of CE using the mathematical model agreed to within 3.5% with experimental data over a range 80.4–93.7%.