Drought stress is one of the most important factors limiting plant growth and productivity in agriculture, as well as reduce turf growth and quality. Turf grass, as an important element of the landscape, is suitable for using in athlatic fields, parks, gardens, and lawns. Turfgrass water use rates often exceed natural precipitation, especially in the arid and semi-arid conditions, growth restrictions may be imposed limiting water that can be applied to turf gareas. As such, researchers have intrested to identify turf species and cultivars that have good drought resistance for reducing water requirement in turfgrass. Restriction of water resources is the main problem of turfgrass in some regions of Iran. Therefore, this study was carried out to evaluate morphological and physiological responses of native tall fescue ( Festuca arundinacea Schreb.)(ecotype Shareh-kord) and perennial ryegrass ( Lolium prenne L.)(blend: Ringles, Lover and Caddishack) to withholding irrigation, as well as investigates the effects of extract sprays of Ascophyllum nodosum (5 mL·L ?1 ; 2 day intervals) on alleviated drought stress in these species. Turfgrass seeds were cultured in PVC pots in a greenhouse. Plants were irrigated daily until drainage occurred. After establishment of plants, irrigation was withholded until leaf wilting of the most plants reached to 90%, and then rewatered. Results showed that growth height, shoot dry weight, turf color, relative water content and chlorophyll content were decreased due to drought stress, but decreasing in ryegrass was less than tall fescue . Tall fescue showed higher root length and root dry weight than ryegrass species. With prolonged stress treatment, electrolyte leakage, malondialdehyde and proline contents increased, but increasing in ryegrass was less than tall fescue. Superoxide dismutase and catalase activities in stressed plants decreased and then increased with prolonged stress. In the 7 day after of withholding irrigation, the activities of these enzymes were more in, tall fescue but with prolonged stress enzyame activities in ryegrass were higher increase. Seaweed extracts increased turf growth, fresh and dry weights of clipping, root length and dry weight, and chlorophyll content in treated plants. There were increases in plant growth and the antioxidant defensive mechanisms such as catalase (CAT), superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities as well as reduced electrical linkage, lipid peroxidation and proline content in the treated plants. Result showed that after irrigation withholding, leaf wilting of tall fescue started sooner than of ryegrass reached to 90% respectively. Recovery of both species increased during rewatering and finally became similar to control plants. Overall, results showed that ryegrass specie showed higher performance tha native tall fescue during prolonged drought stress. Also, our findings imply that several mechanisms including drought tolerance, osmotic adjustment and antioxidant defense systems may interact to enhance the performance of plants in the face of environmental stress following SWE treatments. Key Words : drought stress, seaweed extract, wilting, enzyame antioxidant