The effect of Pseudomonas syringae on morphological and antioxidant enzyme of Lablab purpureus L. (Sweet) was studied. Jasmonic acid are important endogenous chemical signals that play a key role in enhancing plant defense response Pseudomonas syringae cultures were injected into the stem region of 15 days old Lablab purpureus seedlings. Manual injection was found to be successful in inducing brown spot of Pseudomonas syringae. Post treatment of JA given as foliar spray resulted in enhance in the plant defense response. It was found that the level of Peroxidase, Polyphenol oxidase, Catalase and SOD was affected to a level of 85%, 35%, 44% and 60% respectively. Post treatment of JA at 0.5 µM, 1 µM, 2 µM and 5 µM each for 3 days resulted in enhanced resistance to brown spot disease. JA caused alleviation of responses induced by the pathogen in all aspects. Thus, JA treatment was found out to be considerably beneficial in reducing symptoms protecting the Lablab against the pathogen.