Copper (Cu) is a highly essential micronutrient impacting many vital plant physiological processes, such as photosynthesis, enzymatic activity, cellular functions like cell wall formation, mitochondrial respiration, oxidative stress response, and protein metabolism. This study aimed to evaluate the effect of copper oxide nanoparticles (CuO NPs) sprayed onto Swiss chard (Beta vulgaris ssp. cicla L.), kale (Brassica oleracea), and lettuce (Lactuca sativa) leaves grown in hydroponic Ebb systems (electric conductivity of mineral solution 1.3 mS cm^-2, pH 5.5-6.0) in controlled environment chambers (photoperiod of 18 h, day/night temperature 21/17±2 °C, and 60±5% relative air humidity) under the combination of white 65%, blue 5%, red 30% light emitting diodes (LEDs) with two intensities 150 and 250 µmol m^-2 s^-1. The influence was determined on the fresh (FW) and dry (DW) shoot and root biomass, leaf area, chlorophyll and flavanol index, and nitrogen balance index. Swiss chard, kale, and lettuce were sprayed with suspensions of CuO NPs of 10 and 40 nm at a concentration of 30 ppm. Plants that were sprayed with distilled water were considered as control. The results showed that the most effective CuO NPs influence on growth parameters was under 250 µmol m^-2 s^-1 intensity, especially for Swiss chard. The leaf area of such a plant increased by 62% and FW by 56% when sprayed with 10 nm CuO NPs suspension compared with the control. Meanwhile, the lettuce leaf area increased by 25% and kale by 15%. Spraying with CuO NPs suspension positively affected kale DW and chlorophyll content in lettuce leaves. Meanwhile, lower 150 µmol m^-2 s^-1 intensity resulted in more diminutive plants and a lower effect of CuO NPs on their growth rates than plants grown under higher intensity conditions. In conclusion, these results revealed that CuO NPs could be used in plant production to improve growth parameters. Acknowledgments: This project has received funding from the Research Council of Lithuania (LMTLT), agreement No. S-MIP-21-27.