Predicting crop yield response to irrigation level is increasingly important to optimize irrigation under limited available water and for enhancing sustainability and profitable production. This study was carried out to evaluate the performance of CropWat model in predicting deficit irrigation effect on cotton crop, and to explore some alternatives for cotton irrigation. Crop yield and water use data were collected from a 3-yr (2007-2009) field experiment to assess the response of drip-irrigated cotton to deficit irrigation (DI).