Cowpea (Vigna unguiculata) is a crop widely grown in semi-arid regions but faces challenges due to high salinity levels in irrigation water. Management strategies, such as hydrogen peroxide (H2O2) application, promise to mitigate salt stress. This research aimed to evaluate hydrogen peroxide as an attenuator of salt stress in cowpea. The experiment was performed in a randomized block design, in a 3 x 3 factorial scheme, with four replicates. The treatments consisted of three values of electrical conductivity of the irrigation water (0.5, 3.5, and 6.5 dS m-1) and three concentrations of H2O2 (0, 100, and 200 mu M). Growth variables, number and weight of nodules, gas exchange, chlorophyll indices, chlorophyll a fluorescence, electrolyte leakage, and water relations were evaluated. The application of 200 mu M of H2O2 is the most recommended to mitigate the effects of salt stress up to 3.5 dS m-1. Applying 200 mu M of H2O2 mitigated these effects, improving the net CO2 assimilation rate, and cell integrity, resulting in higher biomass and development of cowpea plants. The use of H2O2 enables the development of management strategies aimed at optimizing cowpea growth and tolerance under salinity conditions, possibly by enhancing cellular integrity and mitigating oxidative stress.