A Cu(InGa)Se2 film was modified with CdS/ZnO for application to solar water splitting. Platinum was electrodeposited on the ZnO layer as a hydrogen evolution catalyst. The effects of the electroplating time and acidity level of the electrolyte on the photocurrent density were studied. The highest photocurrent density of -32.5 mA/cm2 under 1.5 AM illumination was achieved with an electroplating time of 30 min at a pH of 9. This photocurrent density is higher than those reported in previous studies. The markedly high performance of the CIGS/CdS/ZnO photocathode was rationalized in terms of its type II cascade structure that facilitated efficient charge separation at the interface junction.