Zinc (Zn) is an important micronutrient that plays roles in several plant physiological processes. The significant role of Zn in tolerance to salinity of certain plants has been associated with plant antioxidant capacity improvement. Zinc-amino chelates have recently been synthesized at Isfahan University of Technology using different amino acids and the effectiveness of these chelates as modern Zn sources on plant growth, yield and nutrients uptake have been investigated. In the present study, the influence of certain amino chelates including Zn(Gly) 2 , Zn(Arg) 2 , and Zn(Gln) 2 on yield and some physiological parameters of two hydroponically-grown lettuce cultivars (Lactuca sativa L. cvs. Lollo Bionda, Lollo Rossa ) at salinity conditions was compared with Zn-sulfate. Lettuce plants exposed to three salinity levels i.e., 0, 20, and 40 mM NaCl. A Zn-free treatment was also considered as control. The experiment was arranged as a completely randomized design with a factorial arrangement with three triplications. One week after transferring to the hydroponic system as the main growth media, lettuce seedlings were exposed to salinity treatments. Different Zn sources were added to the nutrient solution along with applying salt treatments. The plants were harvested after two months and roots and shoots dry and fresh matter weights of 'Lollo Rossa' were measured. Also, concentrations of Zn, Fe, Na, K, Ca, chlorophyll a and b, malondialdehyde (MDA), phenolic compounds and activity of guaiacol peroxidase (GPX) and superoxide dismutase (SOD) in shoots and roots of both lettuce cultivars were determined. The main effects of cultivar, salinity level, and Zn treatment and their interactions on the measured parameters were significant at 0.001. According to the results obtained, Zn-amino chelates enhanced salt tolerance of 'Lollo Rossa'. Addition of Zn-amino chelates resulted in increase of shoot and root uptake of Zn, Fe, K, Ca by lettuce as compared with the Zn-free control treatment. Elevated activity of GPX and SOD enzymes in comparison to the Zn-free treatment were also observed by application of Zn-amino chelates. Application of Zn-amino chelates increased concentration of phenolic compounds in tissues of lettuce plants grown at saline conditions. Among various Zn treatments, Zn(Gly) 2 resulted in the greatest Zn and Fe and the lowest Na concentration of plant tissues. On the other hand, Zn(Arg) 2 had the greatest effect on shoot and root K and Ca concentration. The effect of Zn-amino chelates on activity of GPX and SOD was dependent on the crop cultivar. In 'Lollo Bionda' Zn(Arg) 2 had the greatest effect on increasing root and shoot activity of GPX while in 'Lollo Rossa' the highest activity of the enzyme was achieved with Zn(Gly) 2 . In both lettuce cultivars, Zn(Gly) 2 had the greatest effect on shoot activity of SOD. The effect of Zn-amino chelates on tissue concentration of phenolic compounds also varied upon to the cultivar. In 'Lollo Rossa' Zn(Gln) 2 and in 'Lollo Bionda' Zn(Arg) 2 resulted in the highest concentration of phenolic compounds in plant tissues. Addition of Zn(Arg) 2 significantly reduced lipid peroxidation in shoots of both lettuce cultivars. Among the Zn sources used in this experiment, Zn(Gln) 2 and Zn(Gly) 2 had the highest effect on shoot SOD activity of 'Lollo bionda'. According to the results obtained from this study, it is concluded that Zn-amino chelates Zn(Gln) 2 and Zn(Gly) 2 might be used as effective Zn sources to increase uptake of this nutrient and to improve antioxidant capacity of lettuce under saline conditions. Keywords Zinc, Salinity, Amino acid, Lipid peroxidation, Phenolic compounds, Guaiacol peroxidase, Superoxide dismutase