Two field experiments were carried out during two successive seasons of 2010 and 2011 at the Experimental Farm of El-Kassasin Horticultural Research Station, Ismailia Governorate, Egypt, to investigate the effect of drip irrigation rates (784, 1568 and 2352 m³ water/fad.), biofertilizers rates (control, 500 g nitrobein + 500 g phosphorein, 1000 g nitrobein + 1000 g phosphorein and 1500 g nitrobein + 1500 g phosphorein) and antioxidants (control, citric acid, salicylic acid and glutathione) at rate 100 ppm each, on growth, flowering and chemical constituents of Echinacea purpurea L. plants. The results declared that vegetative growth, flowering and chemical constituents of Echinacea purpurea L. plants were significantly increased gradually with increasing water quantity from 784 up to 1568 m³ water/fad., in both seasons. Moreover, data manifested that raising the application rates of nitrobein and phosphorein to plants, generally, caused a gradual and steady increase in growth, flowering and chemical constituents in both seasons as compared to without inoculation (control). In this respect, inoculation plants at rate of 1500 g nitrobein + 1500 g phosphorein/fad., recorded high values of growth, flowering and chemical constituents than other biofertilizers rates or control treatments. Furthermore, vegetative growth, flowering and chemical constituents were promoted with all spraying antioxidants as compared to control. Spraying plants with glutathione recorded uppermost values of growth, flowering and chemical constituents more than the other antioxidants.