The objectives of the study are to predicate crop coefficient (Kc) for eggplant using watermarks gypsum blocks and atmometer (or ETgage) devices during the growing season and to compare the predicating values of the crop coefficient with FAO recommended Kc and with local study values. The study was conducted in the field within Al-Yusufiya Township, 30km south of Baghdad under semi- arid weather conditions. The watermarks and atmometer were used to measure crop evapotranspiration (consumptive use) and reference evapotranspiration respectively. Watermarks wereinserted in the root zones of eggplant staring from the time of planting till harvest time, with the same time the atmometer was installed in the same field after evaluation and comparison was done with the FAO-56 modified Penman – Monteith equation. Comparison between the predicating crop coefficient that obtained from crop evapotranspiration and reference evapotranspiration and the recommended FAO for Kc values showed thatthe relative error was29.61%, and with mean absolute error was0.2. Moreover, root mean square difference was 0.25. Additionallythe comparison between the predicating crop coefficient with the local study for Kc values showed a relative error of 36.91% and with mean absolute errorwas 0.26.Moreover, the root mean square differencewas 0.31.