Very little is known about street foods in sub-Sahara Africa. We investigated the scope of the street food phenomenon in Nairobi, both in the past and present, with the aim of establishing circumstances surrounding its practice and its function in the urban food supply. We found that street food vending and consumption in Nairobi rapidly increased during the previous two decades, instigated by the need for affordable food among low-income urban dwellers and the need for employment. It is an expanding and thriving phenomenon, especially among the urban poor, and climbs up the socio-economic ladder due to increasing monetary demands. In addition to being a food supply channel for the urban poor, street food vending in Nairobi provides employment opportunities to a labour force that would otherwise be unemployed. There is need to legitimize the sector with simple regulations that make the food safe but not expensive.