In recent years, maize has gained prominence as an important staple crop in Ethiopia second only to teff in terms of acreage. Most of this is grown by semi-subsistence farm households whose livelihoods are tied to crop production and some livestock keeping. Therefore, an important policy question concerns the impact that the reported maize revolution has had on household food security. This paper answers that question by examining the empirical regularities that explain the adoption of improved maize varieties (IMVs) and how this has impacted household food security in a sample of 2327 maize producing households in 39 districts of Ethiopia. An endogenous switching regression model supported by the dose-response continuous treatment effect method was used to empirically assess the impact of IMV adoption on per capita food consumption expenditure and perceived household food security status. Results show that IMV adoption has a robust and positive impact on per capita food consumption and also significantly increases the probability of a smallholder being in food surplus. The advances in the adoption of improved maize has thus contributed significantly to the food security of maize producing smallholders, confirming the role of crop improvement in contributing to food security of agrarian households.