A pot experiment was conducted during the seasons of 2017 and 2018 at Antoniades Research Branch, Horticulture Research Institute, A.R.C. Alexandria, Egypt to study the effects of foliar spray of some vitamins (control, ascorbic acid, α-tocopherol or nicotinamide) at 100 ppm and irrigation intervals (2 or 3 days) on the vegetative growth, flowering, and some biochemical constituents of (Helianthus annuus L.) plants. The results cleared that, most parameters were significantly affected by application of the three vitamins which were used in this study. The magnitude of increase is more pronounced by applying α-tocopherol, where, using α-tocopherol by 100 ppm gave the highest number of leaves and stem diameter, and the lowest proline concentration. Also, using of α-tocopherol by 100 ppm combined with 3 days irrigation interval gave the highest significant increases in the plant height, leaf area, leaves dry weight, stem dry weight, flower duration, flower dry weight, and leaves content of chlorophyll a, chlorophyll b and total carbohydrate. Kakar and Soomro (2001) Therefore, it is advised to use this treatment to provide the amount of water used in the production of the plant and obtaining the highest quality for it.