Nanotechnology holds great potential for improving water quality and controlling water pollution. The distinguishing features of nanosized materials lead to enhanced performances in photocatalytic activity making nanomaterials play a major role in a broad range of applications in water treatment. Nanomaterials can effectively remove noxious and organic pollutants from waste water and can efficiently kill bacteria. As an effective and efficient oxidation process, photocatalysis finds extensive use in the treatment of wastewater. The unique physical and chemical properties of metal oxide nanoparticles make them most versatile materials in the environmental remediation. Nevertheless, there is an urge for developing cleaner, green, and more sustainable methods for the synthesis of nanomaterials by employing cheaper and more ecofriendly methods as compared to the traditional synthesis methods. Therefore, the present chapter explores the studies via plant and microbial-mediated greener synthesis on the preparation of silver oxide nanoparticles. The photocatalytic mechanism as well as the varied photocatalytic applications of silver oxide nanoparticles for their potential use in waste water treatment is also highlighted.