Urban agriculture (UA) initiatives have been increasing in recent years as a nature-based solution for achieving many of the 2030 UN Sustainable Development Goals. However, climate change is expected to have effects on rainfall patterns, which are likely to impact urban food production. The main aim of this paper is to evaluate how issues related to water sources for UA have been addressed in the scientific literature from two different socioeconomic and environmental realities, Brazil and Italy. The method involved a systematic literature review, considering the PRISMA guidelines. The Web of Science database and papers' reference lists were used for retrieving original articles, published in 2000-2020 interval, indexed on scientific databases, and containing data on the typology and quality of water sources used in UA studies. After applying the eligibility criteria, 191 papers were selected - Brazil (108) and Italy (83). The last five years have seen an intensification of studies into issues involving water. Tap water has been identified as an important source of irrigation water for UA, if not the main one. No studies were found that addressed the impact of UA on public water supply systems. The findings point towards more sustainable practices involving the reuse of water and adaptive practices towards water security. We identified that innovative production systems like container farming, aquaponics and indoor agriculture, as well as cultivation of fruit trees, wild edible plants and varieties with low water requirements can represent water-saving options.