In this research the interaction effects of NaCl and nitrogen concentrations, on some physiological, biochemical, and growth characteristics of three olive (Olea europaea L.) cultivars (Abou-Satal, Arbequina and Conservolia) were investigated. The experiment was conducted as factorial with four NaCl levels (0, 40, 80, and 160 mM) along with three (NH₄)₂SO₄  levels (0, 200, and 400 mg L^-1) based on a completely randomized blocks design with three replications. Salinity had a statistically significant negative effect on responses considered, although the severity of the effect varied among cultivars. High concentration of salinity decreased the plant height, leaf number, root and leaf K/Na ratio, N absorption and concentration of root and leaf, K, Ca, Mg and P both of root and leaf while increased the root and leaf Na and Cl concentration. Increasing N levels to 200 mg L^-1 has improved the plant height and leaf number. At 200 mg L^-1 N concentration, Na, Cl and Ca root and leaf were decreased whereas, K/Na ratio, N absorption and concentration also K, Mg and P of root and leaf were increased. It can be concluded that under salinity condition increasing N concentration up to 200 mg L^-1 in salt sensitive cultivars to salinity is favorite in counteracting the adverse effects of salinity but the further increase of N concentration (400 mg L^-1) may be ineffective or harmful for the growth of olive plants. In this experiment, investigation cultivars responses to salinity showed that cv. Abou-Satal is a highly resistant at highest salinity level (160 mg L^-1), also cv. Arbequina is semi-sensitive and cv. Conservolia is a sensitive to salinity condition.