Improving access to healthy foods in low-income neighborhoods is a national priority. Our study evaluated the impact of opening a supermarket in a ‘food desert’ on healthy food access, availability and prices in the local food environment. We conducted 30 comprehensive in-store audits collecting information on healthy and unhealthy food availability, food prices and store environment, as well as 746 household surveys in two low-income neighborhoods before and after one of the two neighborhoods received a new supermarket. We found positive and negative changes in food availability, and an even greater influence on food prices in neighborhood stores. The supermarket opening in a ‘food desert’ caused little improvement in net availability of healthy foods, challenging the underpinnings of policies such as the Healthy Food Financing Initiative.