The present study was performed in a newly reclaimed land at Ali Moubark Farm, South Tahrir Research Station, Horticulture Research Institute, during the two successive growing seasons of 2009/2010 and 2010/2011, to study the effect of four rates of mineral NPK and harvesting dates on the productivity and quality of cassava tuber roots (Indonesian cultivar). The treatments included four different levels of mineral fertilizer NPK namely 50%, 100%, 150% and 200% of the recommended NPK (50 N + 77 P2O5 + 96 K2O kg/fed.) by Sherif et al. (2003), and four harvesting dates (8, 9, 10 and 11 months from planting). Application of NPK fertilizer at rate of 50% significantly produced the highest chlorophyll content in leaves (SPAD), tuber roots yield and average weight of tuber root. On the contrary, the highest rate of 200% NPK increased plant height, leaf area. On the other hand, using rate of 150% NPK increased dry matter yield and percentage, diameter, starch % and starch content yield of tuber roots. NPK percentage in cassava leaves at 180 day after planting, were not affected with any rate of mineral fertilizers. Concerning harvesting dates, the highest yield, dry matter yield and percentage, average weight and diameter of tuber root, percentage and the content of starch in tuber roots were obtained with harvesting at 10 months age, while the harvesting at 8 months had the reverse trend. Applying mineral fertilizer to cassava at rate of 150% NPK and harvesting at 10 months after planting, gave the highest estimated values for tuber roots yield, dry matter yield and percentage, starch yield and percentage. The mineral fertilizer of 50% kg of NPK gave the highest average tuber root weight when cassava harvesting was done at 10 months age. Also, the highest average tuber root diameter was obtained when cassava received 100% NPK and harvested at 9 months age.