Zinc oxide is one of the inexpensive semiconductors with rich electronic and optical properties. It is studied in energy applications for a long time. The wide bandgap of ZnO either needs structural change or sensitizing via quantum dots, dyes, or metallic nanoparticles (through the plasmonic effect) to absorb visible light for applications in solar energy harvesting devices. This review provides a fundamental insight of plasmonic visible light harvesting by ZnO and an account of recent advances in solar photovoltaic, photoelectrochemical water splitting, and other photoredox activities, such as water quality enhancement and CO2 reduction.