Two field experiments were carried out at the Experimental Farm, Faculty of Environmental Agricultural Sciences, Arish University, North Sinai, Egypt during two successive seasons, 2015 and 2016. The experiments aimed to study the effect of deficit irrigation water on soil properties and cowpea production (Vigna unguiculata (L) Walp.) cv. '' Tiba'' grown under loamy sand soil conditions using drip irrigation system. The experiment included three irrigation treatments which were 50, 75 and 100% of irrigation water requirements (IWR). Cowpea seeds were sown on 28th April in first and second seasons. The results showed that the highest decrease percentage from the initial value of soil salinity was obtained with application of 100% irrigation treatment, while the lowest reduction value of soil salinity was found with application of 50% irrigation treatment. The highest value of water use efficiency (WUE) observed was obtained with 50% irrigation level, whereas, the lowest value was with 100% irrigation level. The highest actual evapotranspiration (ETa, mm) was obtained with applying 100% irrigation level during both seasons. Also, the highest value of (WUE) was obtained with 100% irrigation level during 2015 and 2016 seasons. Significant effects were recorded due to irrigation deficit on all vegetative growth traits of cowpea plant in both seasons; viz, plant height (cm), number of branches/plant, number of leaves /plants, fresh and dry weight/plant (g) and leaflet area of 3rd leaf. Decreasing the irrigation level resulted in lower values of all studied traits in both seasons. Irrigation levels caused significant effects on all studied yield and its components traits; viz, seed yield per fed., weight of 100 seeds, pod length, and number of seeds per pod in both seasons. The highest values of all traits were recorded with application of the irrigation level of 100%, while, the lowest value was recorded with 50% irrigation level in both seasons.