A field experiment was conducted in 2013 and 2014 at the Agriculture Experimental Station of King Abdulaziz University to study the effects of water deficit treatments at different growth stages on growth, yield and IWUE on cowpea cultivars. Four water deficit treatments were applied T0 (no water deficit), T1 (at vegetative stage), T2 (at flowering and pod setting), T3 (at pod filling), T4 (at vegetative and flowering) and T5 (at flowering and pod filling). The cultivars 'Balady' under water deficit T 1 , T 3 and T 4 and 'Cream7'under T 1 and T 2 produced the highest yield component parameters except number of pods/plant. The highest yield of dry seeds kg/ha was produced by the cultivars 'Cream7' under water deficit T 1 and T 3 and 'Balady' under T 2 . 'Cream7' and 'Balady' revealed the highest irrigation water use efficiency (IWUE) under water deficit T 1 , T 2 and T 4 . High seed yield of 'Balady and 'Cream7' can be obtained by applying water deficit at vegetative stage (T1).