The effects of irrigation with saline water were studied on barley plants cultivated under arid conditions at the Institute of Arid Regions located in the South East of Tunisia. Two barley accessions (Karkeni and Bengardeni) and three regimes of irrigation as a function of the cultural evapotranspiration ETc (T0: 100% ETc, T1: 75% ETc and T2: 50% ETc) were used. Several parameters – gas exchange (A, E and gs), total flavonoid contents (TFC), total phenolic contents (TPC), phenolic compounds, antioxidant activity (DPPH and ABTS) and grain yield (GY) – were used to assess the effects of the studied factors on barley plants. Gas exchange parameters (A, E and gs) vary significantly between treatments. Salinity stress had no significant effect on TPC and TFC. Phenolic compounds varied significantly between treatments and accessions. In addition, their antioxidant activity based on DPPH and ABTS scavenging assays increased and are more important in Karkeni than Bengardeni under soil salinity. In addition, soil salinity decreased yield and yield components. Karkeni was more productive than Bengardeni.