In order to investigate the effect of nitrogen fertilizer levels, sowing date and harvesting age on growth yield and root quality of sugar beet. Four field experiments were conducted at Mallawi Research Station, El-Minia Governorate during 2015/2016 and 2016/2017 seasons. Sugar beet sown at two dates (the 1st of September and October) fertilized with three nitrogen levels (80, 100 and 120 kg N/fed.) and harvested at three ages (180, 195 and 210 days after sowing). The results showed that all studied traits of sugar beet were significantly affected by sowing date in both seasons. The highest values of root length, diameter, root fresh weight, as well as a-amino N, Na, K, sugar lost to molasses, root and corrected sugar yields were obtained by delaying sowing date from September 1st to October 1st. On the contrary, an higher sucrose, quality and corrected sugar percentages were detected in beets sown earlier in September. Raising nitrogen fertilization level from 80 to 100 and 120 kg N/fed. resulted in a gradual and significant increases in root fresh weight, root length and diameter, root yield, sugar lost to molasses and corrected sugar yield in both seasons. While, alkalinity coefficient and quality percentages were decreased. The highest sucrose and corrected sugar percentages were recorded by applying 100 kg N/fed. The studied traits were markedly influenced by plant age at harvesting in both seasons. Root length and diameter, root fresh weight and yield/fed, sucrose, quality, corrected sugar percentages and corrected sugar yield/fed. were increased gradually with increasing plant age at harvest from 180, 195 to 210 days, in both seasons, while Na, sugar lost to molasses and alkalinity coefficient were decreased. Under these conditions of the present work, sowing sugar beet on October 1st, with nitrogen fertilization at rate of 120 kg N/fed. and harvested at 210 days from sowing could be recommended to obtain the highest root yield/fed., while harvesting it after 195 or 210 days to get the highest sugar yield/fed.