Background: Food security is a topical issue but one that can be difficult to measure. Objective: To develop a community-approved food basket tool and use this to investigate the availability and affordability of a healthy diet in a multicultural urban setting. Design: A 7-day healthy food basket (HFB) containing 96 foods for six household types was developed through focus groups ( n = 6) with local residents recruited via the local health service and community organisations. A total of 41 stores were surveyed against the recommendations of the HFB. The availability and price of core food groups and energy dense discretionary foods were analysed. Setting: A multicultural area in Central London with a high concentration of socially and economically deprived households. Results: Healthy food for a variety of minority ethnic diets was available in the study area, although only one supermarket and three online stores stocked the full basket. Discretionary foods were readily available and often cheaper than healthier options. The largest proportions of cost were attributed to protein foods (30%–38%) and fruit and vegetables (20%–27%). Most foods in the HFB were cheaper at larger supermarkets, although fruit and vegetables cost less at markets and local stores. Total basket price varied greatly between stores, with cost savings achieved when buying from at least three stores. Conclusion: Economically disadvantaged members of the community may be excluded from accessing a healthy diet rather than cheaper foods that are energy dense and low in nutrients, particularly if they are unable to shop around. These findings provide insight for the development of voluntary sector partnership programmes, community education and local policy planning.