The main purpose of this investigation was to evaluate the yield, yield attributes and water use efficiency of Giza 126 barley cultivar under rainfed conditions. Two field experiments were carried out in flood plain of Wadi Hashim, Raas El-Hekma Region, East Mersa Matrouh, Matrouh Governorate, North Western Coast of Egypt, during tow winter growing successive seasons (2011/2012 and 2012/2013) to study the effect of size strip of water harvesting (catchment): cultivated area and (mineral nitrogen and biofertilization) on yield, yield components and water use efficiency (WUE) of barley. Results indicated that, yield and yield attributes of barley i.e. number of spike/m², 1000 grain weight (g), biological yield (kg/fed.), grain yield (kg/fed.) straw yield (kg/fed.) and harvest index were significantly increased with increasing the ratio of catchment area to cultivated area as compared with control (without leaving catchment area) and by increasing mineral nitrogen fertilizer up to 20 kg N/fed. with biofertilization inoculation, but number of tillires/m² significantly increased with increasing the ratio of catchment area to cultivated area only in the second season and by increasing mineral nitrogen fertilizer up to 20 kg N/fed. with biofertilization inoculation in the first and second season. Moreover, the water use efficiency (kg/m³) for grain yield was significantly increased in the applied water harvesting and mineral nitrogen fertilizer with biofertilization inoculation treatments as compared with the control. From the economical point of view, the optimum treatment in terms of increasing barley yield potential under rainfall conditions was the ratio of 4:1 (four times of cultivated area) and the high dose of mineral nitrogen with biofertilization inoculation (20 kg N/fed. with microbein) at Wadi Hashim, Raas El-Hekma Region.