This study was carried out to compare the performance of the FAO AquaCrop and CropWat models in simulating the effects of deficit irrigation on cotton crop. The models were calibrated using data from the 2007 growing season of a field study conducted to assess deficit irrigation effects on cotton, whereas the models were validated by comparing their outputs for yield and water use (ETc) with the measured values of the two variables in the 2008 and 2009. The relationship between measured and predicted values of yield and ETc revealed that the AquaCrop was better than CropWat in predicting water stress impact on yield and ETc. The linear regression equation for AquaCrop had a small intercept and its slope was very close to unity. The index of agreement (d) was close to one for both models, except its value for ETc in the 2009 year. Both models could reproduce the general trend of the changes in soil water content in the different irrigation levels. Accordingly, the use of AquaCrop instead of CropWat should be encouraged for management and planning of irrigation, since it is a practitioner type model keeps a good balance between output accuracy and simplicity.