Two field experiments were conducted in 2018/19 and 2019/20 in salty soil ( ECe 6.86 dS m^-1), on Vicia fabagrown under three irrigation regimes 100%, 80% and 60% of crop evapotranspiration (ETc) combined with three potassium (K) levels (90, 120 and 150 kg ha^-1). The objective was to investigate the effects of potassium fertilizer application on faba beanmorpho-physiological response under water stress. Plant water status (relative water content RWC, membrane stability index MSI), chlorophyll fluorescence (F_v/F₀andPI) and SPAD index had been significantly affected by irrigation or/and potassium application. Potassium improved growth characteristics (i.e., plant height, number of branches per plant, number of leaves per plant, dry matter per plant and leaves area per plant) as well as nutrients contents of (N, P, K, and Ca) and decrease of Na concentration in leaves. Seed yield and water use efficiency (WUE) were significantly affected by irrigation and potassium treatments. Results indicated that potassium application of 150 kg ha^-1 and 120 kg ha^-1 significantly increased seed yield by 33.4% and 18.1%, respectively, compared to (90 kg ha^-1) as average for two seasons. It was concluded that application of higher levels of potassium fertilizer in salt affected soil improves plant water status as well as growth and yield of faba bean under water scarcity.