With increasing urbanization, greywater, generated from domestic activities like bathing and washing, is a marginal water resource that can be valorized to meet irrigation demands and overcome water scarcity. This review paper delves into the characteristics and variability in greywater quality, highlighting the benefits of greywater reuse, such as water conservation, nutrient supply, and potential cost savings, as well as challenges like pathogen contamination and salinity buildup. Various treatment methods, including physical, chemical, and biological processes, are discussed concerning their effective use for irrigation. This paper explores the integration of greywater irrigation with vegetated walls, an innovative urban greening solution that offers numerous environmental and social benefits. The types of vegetated walls, their irrigation requirements, and studies involving greywater application in these systems are discussed. By synthesizing the current knowledge, this review article provides a comprehensive understanding of enhancing urban sustainability through the valorization of an otherwise wasted resource.