Urban sites gather poverty in particular locations and often require bulk food system approaches for addressing prevalent food security and nutrition needs. The food systems that service them are, however, characterized by perishability and large irregularities in supply. Seafood is currently recognized as contributing in a major way to food security and nutrition, and it is to assessing the role of wholesale markets in meeting the needs of the urban poor that this paper is directed. It zooms in on the city of Chennai, India, where an estimated 40% of the population is considered poor and marine fish plays a crucial role in diets. Building on one-and-a-half years of field research in the pre-COVID-19 period, the paper analyses the performance of one of the city’s largest fish wholesale markets, Vanagaram, in relation to the four commonly recognized pillars of food security. Results demonstrate how urban food systems function as major suppliers of fish (and other food items) to thousands of low- and middle-income households. Most importantly, this case study demonstrates the crucial role that is played by wholesale markets in merging low-price fish supplies from different geographic regions and thereby ensuring food security of poorer inhabitants.