Powdery mildew disease, caused by Erysiphe cichoracearum, is considered one of the most severe pathogenic threats of sunflower worldwide. This study discusses how to improve the effect of biocontrol agents, as a more economic and eco-friendlier alternative to fungicides, by mixing different bioagents (Trichoderma harzianum and Bacillus subtilis) with different antioxidants (ascorbic acid and salicylic acid), either individually or combined. They were applied to sunflower during two successive seasons to determine their effectiveness in promoting growth and inducing resistance in sunflower against powdery mildew disease under field conditions. Results show that all treatments reduced the severity of powdery mildew disease significantly compared with control. A synergistic effect was noticed when combining T. harzianum and salicylic acid led to a significant decrease in powdery mildew disease severity in sunflower in comparison to control. In general, the results suggested that the integration of antioxidants with bioagents showed a better response to control powdery mildew disease than single treatments. In field experiments, the applied treatments significantly increased all of the studied growth parameters, plant length, fresh and dry weight. All treatments showed a remarkable increase in physiological aspects (enzymes activity and total phenol content).