In order to study the effect of foliar spraying times and levels of yeast extract and boron on productivity and quality of sugar beet cv. Hossam, a field experiment was carried out at Kalabsho Experimental Farm (sandy soil), Dakahlia Governorate, Sugar Crops Research Institute, Agricultural Research Center, Egypt, in two successive seasons of 2014/2015 and 2015/2016. Two experiment trails were laid-out in strip-split plot design with four replications. The vertical-plots were assigned with times of foliar application with yeast extract and boron (after 75 and 90 days from sowing). The horizontal-plots were occupied with foliar spraying with yeast extract levels i.e. without spraying (control treatment), spraying with 2, 4 and 6 g yeast/liter. The sub-plots were allocated to foliar spraying with boron levels (control, 100 and 200 mg boron/liter). The results showed that delaying spraying sugar beet plants with yeast extract and boron from 75 up to 90 days from sowing resulted in gradual and significant increases and recorded the highest value for each of root and top fresh and dry weights/plant, root dimensions, purity and sucrose percentages, root and sugar yields/fad., as well as the decrease in the values of sodium, potassium and α-amino nitrogen percentages of sugar beet juice. The best results of yield components, root juice quality parameters and yields were resulted from foliar spraying sugar beet plants with yeast extract at the rate of 6 g/liter in both seasons. The highest values of all aforementioned yield components, root juice quality parameters and yields were obtained as a result of spraying sugar beet plants with 200 mg boron/liter in both seasons. It can be recommended that spraying sugar beet plants after 90 days from sowing with 6 g yeast extract and 200 mg boron/liter to maximize sugar beet productivity and quality under the environmental conditions of sandy soils.