Pot experiments were conducted in a greenhouse with the aim to study the role of antioxidant ascorbic acid under two levels (0 and 100 ppm) in minimizing and/or overcoming the phytotoxic effects of H2S (0, 50 and 100 ppm) on growth characters, some physiological and biochemical aspects; and yield quantity and quality parameters of lettuce plants. Vegetative growth parameters of H2S-polluted lettuce plants were significantly reduced with increasing the H2S level. The phytotoxic effect of H2S at the high level was more pronounced and greater in head length (-31%), stem length (-34%), leaf area (-42%), fresh whole plant (-35%) and dry whole plants (-34%) matters of lettuce plant than other growth characters. Treating the H2S- polluted lettuce plants with ascorbic acid not only counteracted the harmful effect on the above-mentioned parameters, but also induced a greatly increase in them, head length (40%), stem length (104%), leaf area (82%), fresh whole plant (148%) and dry whole plant (96%) matters compared with the untreated plants. Leaf water deficit (LWD), osmotic pressure and membrane integrity (MI) were increased, whereas total water content (TWC), relative water content (RWC), transpiration rate, and the administration of H2S reduced the succulence of the leaves. Using ascorbic acid led to regulate and improve the plant water status by increasing RWC (66%) and osmotic pressure (16%), and decreasing LWD (40%), and MI (28%). All H2S levels had a deleterious effect on leaf photosynthetic pigments; chlorophyll a, b and total chlorophylls, carotenoids, total photosynthesis as well as chlorophyll stability index (CSI). Application of ascorbic acid overcame the inhibitory effect of H2S and enhanced the biosynthesis and concentration of photosynthetic pigments; chl. a (170%), chl. b (303%), total chlorophyll (186%) as well as carotenoids (64%). Exposure of lettuce plants to H2S pollutant significantly reduced the head yield, more at 100 ppm (-50%) than that at 50 ppm (-33%). The values of chemical components, i.e., vitamin C, total protein, total soluble sugars (SS), total amino acids and N, P, K minerals contents in head lettuce leaves significantly decreased with increasing the H2S level. While the Sulphur (S) contents, soluble phenols, NO3-N and NO2-N in lettuce leaves were increased as H2S rates increased. Adding ascorbic acid to the H2S-polluted lettuce plants not only led to overcome the deleterious effect of intolerable H2S levels (50 and 100 ppm) on most above-mentioned characters, but also increased the yield (150 and 169%) and improved the qualitative characters of head lettuce leaves.