Abstarct: Among the abiotic stresses limiting tomato production and productivity, especially during the seedling period, are water shortage, salinity of water and agricultural land. In this study, the effect of ellagic acid at concentrations of 0, 75 and 150 mg/L on tomato plant seedlings under salinity stress at concentrations of 0 and 250 mM was studied. After two weeks, the examination of morphological traits showed that salinity stress had a significant effect on leaf number, leaf area, root length and root weight. Ellagic acid also had a significant effect on leaf area. Although salinity had a stimulating effect on the aerial part, it reduced the length and weight of roots. After 12 hours, the relative exxpression of SIKEA6, SICH18 and SINHX3 genes and biochemical traits were examined. The results showed that the exxpression of the SIKEA6 gene increased with increasing ellagic acid concentration and salinity. Also, the relative exxpression of the SICH18 and SINHX3 genes was similar to the SIKEA6 gene. The results of biochemical traits showed that the interaction between ellagic acid and salinity treatment had a significant effect on the activity of catalase, guaiacol peroxidase and superoxide dismutase and the amount of malondialdehyde and proline. The highest amount of catalase was observed in the treatment of 250 mM salinity alone and in combination with 150 mg/L ellagic acid. In this experiment, the activity of guaiacol peroxidase did not show a significant difference in all treatments and only decreased in the treatment of 150 mg/L ellagic acid. The activity of guaiacol peroxidase decreased with the use of both concentrations of ellagic acid under salinity stress. The amount of malondialdehyde decreased with the use of ellagic acid alone and under salinity stress. The amount of proline decreased with the highest concentration of ellagic acid, 150 mg/L. Overall, baxsed on the positive effects of ellagic acid, it is recommended that further studies be conducted on the effect of ellagic acid as an antioxidant in salt stress in tomatoes at different growth stages.