Abstract: The main objective of this study was to study the performance of alfalfa under water stress conditions and determine water use efficiency (WUE) for optimal forage production under the arid climatic conditions of Al-Ahsa having limited irrigation water supplies. Plant growth parameters of alfalfa were significantly affected by different irrigation treatments. Mean alfalfa dry forage (hay) yield ranged between 2.21-5.33 MG ha-1 in different irrigation treatments. The WUE was higher in T1 (irrigation at field capacity soil moisture level) than other water stress treatments. It was noticed that alfalfa dry forage yield was severely affected by irrigation stress. In conclusion, the WUE of alfalfa crop was highest in T1 (irrigation at field capacity level of soil moisture) than other irrigation treatments. The study provided an excellent opportunity for scheduling irrigation of alfalfa crop for optimal dry-forage production under arid climatic conditions of Al-Ahsa, Saudi Arabia.