The role of defects in transformation of hydrogen-treated ZnO nanorods into visible light-driven material for photoelectrochemical application was investigated. It was discovered that simultaneous generation of zinc and oxygen vacancies led to improved absorption in UV/vis spectra and enhanced photoelectrochemical efficiency under solar and visible lights. The origin of such improvement is mostly attributed to the formation of disordered states and co-generation of zinc and oxygen vacancies which create transition levels within the band gap and facilitate more efficient transfer of photoexcited charge carriers. Hence, the dominant role of only one type of defect on the improved performance of hydrogenated ZnO is reconsidered.