Background and Objective: Seagrass extract is a natural plant biostimulant which can be utilized for enhancing plant growth at various stages. The present study was undertaken to explore the application of Zostera marina seagrass extract as foliar spray on salt stressed tomato plants under green house conditions. Methodology: The one set of green house grown tomato plants were sprayed with seagrass extract and another set with water on 15th day of salt treatment. The accumulation of reactive oxygen species, antioxidant enzyme activities and their physiological responses towards different concentration of salt stress were examined after the 3rd treatment. Data were analyzed by one-way ANOVA using SPSS software version 17. Results: The initial studies revealed that the salt stressed plants shown variation in physiology, Relative Water Content (RWC) and accumulation of hydrogen peroxide (H₂O₂) in the leaves. The activities of ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT) were found to have increased in seagrass extract sprayed plants when compared with the plants sprayed with water. In contrast to APX, SOD, CAT, the activities of peroxidase (POX) were declined in the seagrass treated plants. Conclusion: After 30 days, the plants sprayed with seagrass extract were more efficient in controlling the damage caused by the stress and it has shown enhanced activities of tolerance to the salt stressed plants compared to the control. Further, presence of functional groups and constituents were found in seagrass extract through FTIR and GC-MS analyses.