The experiment was carried out at the Baramoon Experimental Research Farm, Dakahlia Governorate, Egypt, during 2015 and 2016 seasons. The aim of this research was to study the effect of potassium sulfate and calcium borate as soil and foliar fertilization on improving the quality and flower production of Dahlia pinnata, L. plants. Different levels of potassium sulfate at 10 and 20 g/plant as soil fertilizer and calcium borate at 5 and 10 cm/L as foliar fertilizer and companions between them were used. The soil and foliar fertilizers were applied 3 times during the growing period. The results indicated that the combined treatment of 20 g/plant potassium sulfate + 10 cm/L calcium borate significantly increased vegetative growth parameters i.e plant height, number of leaves, number of shoots, stem diameter and dry weight % of plants. It also induced an increment in flowers and tubers parameters (No. of flowers, flower diameter, flower stem length and diameter and flower adherence strength, vase life, No. of tubers/plant and tuber diameter compared with the other treatments used. Total carbohydrates and lignin (%) in flower stem were significantly increased as a result of different fertilization treatments compared to the control treatment. Application of potassium sulfate at 20 g/plant + calcium borate at 10 cm/L was superior to other treatments under this study.