The lack of consensus on the role of the agricultural sector in poverty reduction and pitfalls in impact study methodologies resulted in mixed findings on impact of irrigation. This study explores factors that determine farmer s decision to irrigate and whether access to irrigation water enhances livelihood of the farmers. Cross-sectional data from a survey of 240 smallholder farmers in Wondo Genet, Ethiopia was used for the analysis. Foster-Greer-Thorbecke indices indicated high poverty level among farmers without access to irrigation. Further analysis was undertaken using an endogenous switching regression (ESR) model. The correlation coefficient results proved the existence self-selection and endogeneity. Accordingly, variables like scheme governance, level of water scarcity, and access to network found to be some of variables that significantly affected the farmers decision to irrigate. Model estimates further indicated that access to irrigation resulted in better life conditions when compared to counterfactual situation. Farm income of the households has increased by 107% and 171% for irrigation users and non-users, respectively. Similarly, per adult equivalent consumption expenditure has shown increase by 26% and 57% for irrigation users and non-users. Key Words: Agriculture, Irrigation, smallholder, Wondo Genet, Ethiopia, Endogenous Switching Regression, poverty, Farm income, Consumption Acknowledgement :