This article studies the informal sale of vegetables in the urban space of Hanoï City, Vietnam, a phenomenon that has been little studied in the economic literature until now. In order to analyse the role and the scope of informal selling, we carried out a spatial screening of Hanoï, mapped the distribution of informal vendors. We then interviewed them to understand their selling and adaptation strategies in the urban context. In results, the presence of many street markets of different sizes, significantly correlated with population density, shows, both their functional and structural characters in the city’s food system. Four profiles of informal vendors have been distinguished in regard to the diversity of situations and strategies, which show the importance of the intermediation role of these actors in the supply of Hanoï despite the lack of recognition of their status by the administration. This census also shows the importance of proximity regarding the city’s food supply chains. Informal vendors play a key role in developing close relationships with vegetable suppliers. They are able to transport food products rapidly and make them available close to the consumers. Transactions are frequent and, as in a recurring game, trust relationships are established. These complex links combine legal and illegal, written and oral contracts, officials and under-the-table payments, rules that can be referred to as proximity governance. This is one of the main reasons why informal food selling practices persist, despite the modernisation policy of developing infrastructure of food markets and shopping outlets in Hanoï.