This study aimed at identifying the determinants of Rainwater Harvesting (RWH) technology adoption for irrigation and farmers practice in water harvesting against drought in Gursum district, Eastern Hararghe zone. The specific objectives were assessing farmer's perception towards the RWH technology and determining the major factors affecting adoption of RWH technology by smallholder farmers in the study area. The data was collected from both primary and secondary sources. The primary data for this study was collected from 150 farmers through application of appropriate statistical procedures while secondary data was gathered from various sources like zonal and district Bureau of Agriculture and Rural Development and district of water bureau. This study has used multi-stage sampling technique in which both purposive and random sampling techniques were applied to select the required sampling units from the total population under study. Likert Scale was employed to measure the perception of respondents towards RWH technology, and binary logit model was used to analyse the factors that affect RWH technology. Both descriptive and econometric data analysis techniques were applied. Logistic regression estimation revealed that farm experience of household head, education level, family size, labor availability, distance to market, Total Tropical Livestock Unit (TTLU) perception and external support have significantly affected the RWH technology adoption decision of households in study area. The finding of this study indicated that any effort in promoting and adopting of RWH practice should recognize the socio-economic, technique, institutional, physical and psychological characteristics for better adoption of RWH technology. Taking the specific characteristics of farmers into account in introducing and promoting RWH may help policymakers to come up with projects that can easily accepted by farmers.