We investigate how the development of supermarkets and public markets in a large, rapidly urbanizing African city can shape the equitability of the food system. Using remotely sensed retailer location and population datasets, we analyze the spatial–temporal development of supermarkets and public markets in Lusaka, Zambia from 2004 to 2020. As Lusaka’s population grew by 116%, we found that supermarkets increased from 9 to 54 (500%) while public markets increased from 52 to 65 (25%). Using SaTScan spatial–temporal analysis, we identified seven significant areas of high supermarket development (p < 0.05) clustered from 2013 to 2020 in lower density, higher income residential areas. During this period ten new community public markets were established, suggesting a lack of direct involvement by the government to establish public markets at a pace similar to population growth. Supermarket development without concomitant development of public markets can negatively impact food system equitability in two ways: 1) supermarket development is spatially uneven, favoring more food secure residential areas, thus limiting food access; 2) supermarket development is outpacing the establishment of public markets, which have more favorable food purchasing conditions for low-income households. Improving food security in rapidly growing Southern African cities will require policies that promote retailer diversity and aim to improve urban food system resilience and equitability.