A study was carried out in the 2017 and 2018 cropping seasons, to determine the effect of deficit irrigation and stressed growing stages on the green pea yield and water use efficiency under semi-arid climatic conditions of Elbayda, Libya. Irrigation treatments included (IR100: 1 time potential crop evapotranspiration (ET_c), IR90: 0.9 ET_c, IR80: 0.8 IR70 and 0.7 ET_c, ET₄), and stressed-growing stages included vegetative (V), flowering (F), pods (P) and all stages (A). It is clear from the results that the water regime affected the growth and yield of the pea plants. Both the level of deficit and its timing during the plant life had an effect on the plant growth indicators and the final plant yield. In general the yield decreased as the deficit level increased but the water use efficiency increased with mild water deficit (IR90) then decreased as the deficit level increased. The drought stress during the flowering stage resulted in an increase in the final yield of the pea plants. The water regime to achieve the highest water use efficiency (WUE) while minimizing the water use is 80 % ET_c during the flowering stage (IR80). The highest value of yield production would be at 90% ET_c during the flowering stage (IR90F).