In recent years, water availability is becoming a main issue, due to population increase, urbanization and extensive water pollution. In this context, Nature Based Solutions (NBSs) represent an alternative solution to traditional wastewater treatment technologies that can be effectively applied in urban areas. Among different NBSs, green walls can be efficiently applied on unused building surfaces in urban areas. Furthermore, they provide multiple benefits, such as thermal, naturalistic, economic, environmental and social. Greywater is the portion of wastewater with the highest potential in terms of in situ water reuse for non-potable purposes, since it is available in high quantity with low pollutant content.