A central feature of the transformation of urban food systems in cities of the Global South is the growing presence of supermarkets and their supply chains, often termed supermarketization or a supermarket revolution. A key issue in the African context is whether supermarkets are a threat to other sources of food including informal sector vendors. Most research on the supermarket revolution and competition with other food retailers focuses on large urban conurbations with little attention paid to the role of supermarkets in secondary urban centres. This paper aims to rectify this situation through a case study of the role of supermarkets in three smaller urban centres in Northern Namibia. The paper uses data from a representative household food security survey in 2018 which collected detailed information on household food consumption and food purchasing patterns. We show that supermarkets have established a dominant role in the local food system and are patronized by almost all households. However, the informal food sector displays considerable resilience and is patronized on a regular basis by low-income households. Future research on the impact of the secondary supermarket revolution should examine the experience and strategies of informal food vendors and whether the relationship with supermarkets is truly symbiotic or not.