Boron nutrient plays an important role for crop growth and production. However, the adequate amount of nitrogen and boron that improves plant production and nitrogen use efficiency is still remaining unknown particularly under sandy soil. Thus, field experiments were conducted in two consecutive growing seasons (from 2016 to 2018) at the Experimental Farm at the Nuclear Research Center, Atomic Energy Authority, Inshas, Egypt to investigate effects of boron foliar nutrition and nitrogen fertilizer rates on growth, yield, and nitrogen utilized by onion plant cv. Giza 20. The experiment was laid out in randomized complete block design with six levels of boron (Control, 0.8, 1.6, 2.4, 3.2 and 4 ppm), and three rates of nitrogen (40, 60 and 80 kg N/fed.-1 as ammonium sulphate) in reclaimed sandy soil. The results showed that boron at 2.4 ppm interacted with nitrogen rate at 80 kg N/fed.-1 significantly increased fresh and dry weight g/plant, total chlorophyll content (58.67 and 58.00 mg/g dry weight), biological yield (2.53 and 2.80 kg/m2), economical yield (2.23 and 2.30 kg/m2) and nitrogen utilized percentage (38.25 and 37.68 %) in the two growing seasons respectively. Foliar boron application at rate of 3.2 and 4.0 ppm with all nitrogen rates significantly decreased all the studied character. On the contrary, Potassium and boron content in the bulbs were increased as the boron application rate increased.