Alfalfa is the most important forage plant in Iran and the world. Salinity affects the yield and quality of this crop. Rhizobium is the most known alfalfa symbiont bacteria. Arbuscular mycorrhizae also have the ability to coexist with a wide range of plants. The aim of this study was to investigate the ability of these microorganisms individually or in combination to reduce the negative effects of salinity stress. A pot experiment was conducted to investigate the interaction effects of three salinity levels (0, 60 and 120 mM sodium chloride) and six rhizobium and fungus inoculation treatments (non-inoculation, rhizobium, Funneliformis mosseae , Rhizophagus intraradices , rhizobium+ F. mosseae and rhizobium+ Rh. intraradices ) on alfalfa plants. Treatments were arranged as factorial in a randomized complete block design with four replications. Salinity in most cases decreased root mycorrhizal colonization, relative leaf water content (RWC), the concentrations of potassium and phosphorus, K/Na ratio, plant height, leaf area, shoot and root dry weight and root volume but increased the concentrations of sodium, hydrogen peroxide (H 2 O 2 ), malondialdehyde (MDA), proline, protein, sodium and the activities of catalase (CAT), peroxidase (POX) and ascorbate peroxidase (APX). The extent of increases due to salinity were greater in CAT than in POX and APX. Inoculation of plants with rhizobium alone increased plant height, leaf area, shoot and root dry weight, root volume, the concentrations of chlorophyll, protein, potassium and phosphorus, K/Na ratio and the activities of CAT and APX but decreased the concentrations of sodium, H 2 O 2 , MDA and the activity of POX. Inoculation with F. mosseae did not make significant changes in most of the tested traits, but its combined inoculation with rhizobium increased plant height, leaf area, shoot dry weight, the concentrations of carotenoids and protein and the activities of CAT and APX but decreased the concentrations of sodium, proline, H 2 O 2 , MDA and the activity of POX. Inoculation with Rh. intraradices increased RWC, plant height, leaf area, shoot and root dry weight, root volume, protein content and the activities of CAT and APX but decreased the concentrations of proline and MDA and the activity of POX. Among the tested inoculation treatments, the co-inoculation of rhizobium with Rh. intraradices had the best positive performance. This treatment decreased the content of MDA and H 2 O 2 and increased RWC and the concentrations of protein, phosphorus, potassium, carotenoids and the activities of CAT and APX which ended up increases in yield and yield components. The results of this experiment showed that inoculation with mycorrhizal fungi improves the symbiosis ability of rhizobium bacteria with alfalfa plants. Keywords: Alfalfa, salinity, rhizobium, mycorrhizae, Funneliformis mosseae , Rhizophagus intraradices .