The photoelectrochemical properties of a GaN:ZnO solid solution coated as an electrode on conductive glass are investigated through measurement of voltammograms and current-time curves. The highest photocurrent was achieved by a GaN:ZnO sample with relatively high zinc concentration (Zn/Ga = 0.42) and small particle size, presumably due to more efficient electron transfer through the porous electrode. The electrode exhibits anodic photocurrent under visible light, indicating functionality as an n-type semiconductor electrode. The estimated band-gap position of GaN:ZnO is located at satisfactory potential for water splitting. The bottom of the conduction band is similar to that for GaN, while the top of the valence band is substantially higher than that of either GaN or ZnO. The evolution of H 2 and O 2 is confirmed during photoelectrolysis at +0.5 V vs. Ag/AgCl. The efficiency of photoelectrolysis is found to decrease with irradiation time due to degradation of the electrode.