Drought is a global problem in agriculture, which reduces the productivity of plants so is important environmental stress affecting plant metabolism and growth. In view of the increasing water scarcity related to climate change, there is a need for safe treatment that will contribute to increasing agricultural efficiency. Quercetin is a flavonoid with strong antioxidant properties and plays an important role in regulating the physiological processes in the plant. The study investigated the effect of the exogenous quercetin-copper complex (0.01, 0.05 and 0.1%) on wheat seedlings subjected to drought (30% f.w.c.). A pot experiment was performed to determine the effect of this biostimulator and to select the most effective concentration. Spraying with quercetin derivative solutions was performed twice, and physiological measurements (chlorophyll content and fluorescence as well as gas exchange) were carried out after the first and seventh day after each application. It was shown that drought stress had a negative effect on the photosynthesis process of plants. The application of spraying with a quercetin derivative caused an increase in the values ​​of the parameters in wheat plants subjected to drought stress compared to the control, which was manifested by an increase in the values ​​of chlorophyll fluorescence parameters (F_v/F_m, F_v/F₀ and PI), gas exchange (P_n, g_s and E) and total antioxidant capacity. It was found that the highest dose of quercetin derivative tested (0.1%) had the best effect on plants subjected to drought stress, therefore it is necessary to conduct further research on the use of higher doses of this flavonoid.