Irrigated agriculture has been popularized as a key factor to improve crop yields and enhance food security in Africa. However, empirical findings are mixed. This study analyzes determinants of small-scale irrigation adoption and the impact this may have on food security in Ethiopia, where agricultural land is extremely fragmented and densely populated. Data were collected from 240 farmers, and the findings from the survey were triangulated with focus group discussions and key informant interviews. First, the Foster-Greer-Thorbecke indices indicated high poverty levels among farmers without access to irrigation. Second, accounting for a self-selection bias by using the endogenous switching regression (ESR) model, scheme governance, perceived water scarcity, and access to information were found to have significant effects on the adoption of irrigation schemes. Model estimates further indicated that access to small-scale irrigation resulted in better living conditions for both current users and non-users when compared to their counterfactual situations. Farm income of the user households would decrease by 42% (birr 151,419 or US$ 5,500 per ha) had they not used irrigation. Similarly, farm income of the non-users would increase by 149% had they used irrigation. Per adult equivalent consumption expenditure has also shown a decrease of 35% for irrigation users and an increase of 40% for non-users compared to their respective counterfactual situations. We conclude that much of the perceived water scarcity level is attributed to existing governance regimes more than the physical scarcity of water. The study draws several implications for household food security and local-based water use policies.