Abstract Objective: To identify factors associated with food purchasing decisions and expenditure of South African supermarket shoppers across income levels. Design: Intercept surveys were conducted, grocery receipts collated and expenditure coded into categories, with each category calculated as percentage of the total expenditure. In-supermarket food quality audit and shelf space measurements of foods such as fruits and vegetables (F&V) (healthy foods), snacks and sugar-sweetened beverages (SSB) (unhealthy foods) were also assessed. Shoppers and supermarkets were classified by high-, middle- and low-income socio-economic areas (SEA) of residential area and location, respectively. Shoppers were also classified as “out-shoppers” (persons shopping outside their residential SEA) and “in-shoppers” (persons shopping in their residential SEA). Data were analysed using descriptive analysis and ANOVA. Setting: Supermarkets located in different SEA in urban Cape Town. Participants: Three hundred ninety-five shoppers from eleven purposively selected supermarkets. Results: Shelf space ratio of total healthy foods v . unhealthy foods in all the supermarkets was low, with supermarkets located in high SEA having the lowest ratio but better quality of fresh F&V. The share expenditure on SSB and snacks was higher than F&V in all SEA. Food secure shoppers spent more on food, but food items purchased frequently did not differ from the food insecure shoppers. Socio-economic status and food security were associated with greater expenditure on food items in supermarkets but not with overall healthier food purchases. Conclusion: Urban supermarket shoppers in South Africa spent substantially more on unhealthy food items, which were also allocated greater shelf space, compared with healthier foods.