This research aimed to identify knowledge level of Agricultural Extension agents in Nineveh governorate with water harvesting technology. And identify knowledge level of Agricultural Extension agents in domains ,and items of the test. And identify the correlation between knowledge level of Agricultural Extension agents in domain of water harvesting and some independent variables. Research sample included (103) respondents, representing for (25%) of the population (the Nineveh Agriculture directorate and its agricultural divisions).selected as randomly sample and data were collected through questionnaire consisted of two parts, the first part included measuring the in independent variables, while the second part items of knowledge level of Agricultural extension agents in domain of water harvesting and the number of (28) items from which distributed into four domains in technology of water harvesting. Validity was measured by using face validity and content validity, reliability was tested by Cronbach’s Alpha method which was (0.88). The data had been analyzed by using: means - Pearson correlation coefficient – spearman Brown coefficient . results showed that (87.37%) of the respondents possess a medium knowledge that tends to low. The Results also showed that highest knowledge level of Agricultural Extension agents was in two domains (Comparative advantage, the Maintenance). The research showed that there were significant relationship between knowledge level of Agriculture extension agents and variables (education level, location of work, duration of employment, agricultural information source). and the study recommends To intensify extension efforts in disseminating knowledge in domain of water harvesting through various media, and work to open an agricultural center specializing in water harvesting in the province.