In order to investigate the effects of salt stress on biochemical and physiological responses of two cultivars of alfalfa (Medicago sativa L.) namely, Diabolourde and Yazdi, chlorophyll content, growth parameters, and proline contents of roots and shoots, reducing sugars contents of roots and shoots, and membrane injuries of the plant samples were subjected to 0, 100, 150, and 200 mM NaCl treatment in a factorial experiment based on a completely randomized block design. Findings showed that chlorophyll content, root dry weight, and shoot dry weight decreased in both cultivars under salt stress (p≤0.05). The reduction rate was more severe in Diabolourde cultivar than Yazdi. The root to shoot ratio had no significant differences in Diabolourde while increased significantly in Yazdi under 150 and 200 mM NaCl in comparison with control (p≤0.05). Reducing sugars content and proline content of roots and shoots increased significantly in both cultivars. The enhancing rates were more severe in Yazdi than Diabolourdeh. Also, the electrolyte leakage as a marker of membrane injuries increased in both cultivars as the enhancing rate was higher in Diabolourde cultivar in comparison with Yazdi. These findings showed that Yazdi cultivar employed resistance mechanisms more effectively than Diabolourde and therefore, it suffered lower injuries; higher growth parameters and lower membrane leakage in Yazdi cultivar are in agreement with this claim. According to the findings, Yazdi cultivar is proposed as a more tolerant variety for cultivation in saline area. Manuscript profile