Considering the water situation in the country, the use of modern irrigation systems, including subsurface drip irrigation, is essential to reduce evaporation and increase water productivity. Therefore, this project was conducted in three replications and for 2 years in order to investigate the effect of different irrigation levels on yield and water productivity in a randomized complete block design at the Ekbatan Research Station located in the Agricultural and Natural Resources Research and Education Center of Hamadan Province. The studied treatments included 4 irrigation treatments: 1- full irrigation (providing 100% of the water requirement), 2- deficit irrigation with 85% of the water requirement, 3- deficit irrigation with 70% of the water requirement, and 4- over-irrigation with 115% of the water requirement. Water requirement during the growing season was calculated using the Penman-Monteith formula and ETo Calculator software.The effect of different water treatments on crop yield and water productivity was significant, the highest crop yield was related to the two treatments of 100 and 115 percent of water requirement with yields of 16607 and 17275 kg/ha, respectively, although no significant difference was observed between these two treatments in terms of crop yield.In terms of water productivity, the two treatments of 85 and 100 percent of water requirement had the highest water productivity with 1.94 and 1.99 kg/m3, respectively, and were placed in the same statistical group.By increasing the percentage of water supply from 70 to 100%, a sigmoidal increase in water productivity was observed. However, by changing the percentage of water supply from 70 to 100percent, a sharp decrease in water productivity was observed.Therefore, it is recommended to provide 85% of the water requirement in order to achieve the highest water efficiency in subsurface irrigation of alfalfa.