Groundnuts are an important crop for Ugandan smallholders since they are high in protein, resupply nutrients to the soil, and are a storable source of wealth once dried. Adoption of improved, virus-resistant seed should have a positive impact on household food security, as yields are expected to increase leading to more food for either sale or consumption. This paper considers the effect of improved groundnut seed on smallholder food security in Eastern Uganda, with emphasis on the high adopting Teso sub-region using a household data set collected in 2011. Model results indicate that adopters significantly increase household food security as measured by the World Food Programme food consumption score index in the Teso sub-region, where the scores of adopters increase by nearly 18 points (6.5 percent)—the equivalent to consuming pulses six days. But food security does not increase in other regions of Eastern Uganda where aggregate rates of adoption are lower. Differences in impact on food security between regions of high and low adoption suggest careful consideration of current conditions in policy responses to improve household well-being.