Abstract: Nearly half of the wastewater generated in Nairobi ended up treated in the treatment facilities. However, cases of irrigating vegetables with raw influent and untreated wastewater water by urban and peri-urban farmers in Nairobi have been noted. Despite the importance of wastewater in in Kenya’s urban and peri-urban agriculture, information on the quality of water used for irrigation areas is lacking. This study sought to establish physicochemical and microbiological composition of water used for irrigating vegetables in Ruai ward, Nairobi County, Kenya. A preliminary survey was conducted to identify sources of water used for irrigation. Sources of water used for irrigation were then categorized into the treated effluent, raw influent and wastewater-polluted water sources. From these sources sampling points were randomly selected and georeferenced.