Abstract: This research was carried out to study the inductive role of vit. C and its mode of application in mitigating the detrimental effects of irrigation with diluted (10, 20 and 30%) seawater on Vicia faba L. cv. Hassawi plants. The results showed that, seawater level at 10% exhibited insignificant changes, while the higher levels impaired growth by reducing seeds germination, dry weights of shoot and root, water status and chlorophyll contents. However, seawater irrigation enhanced carotenoids, antioxidant enzyme activities, MDA and ion leakage. The detrimental effects imposed by seawater were ameliorated by application of 100 ppm vit. C either by seed soaking or shoot spraying. Shoot spraying method gave the best effect. The inductive role of vit. C was associated with improvement of seed germination, growth, plant water status, carotenoids, endogenous ascorbic acid and antioxidant enzyme activities, which consequently led to reduction in ion leakage and MDA level. Moreover, vit. C alone or in combination with seawater increased the intensity of protein bands as well as synthesized additional new proteins with molecular weights of 382, 154, 132, 106 and 67 kDa. This may lead to an increase in the tolerance mechanisms of treated plants towards seawater salinity.