Cadmium nanoparticles (NPs) used in semiconducting devices are photosensitive and optically active. The objective of this study was to investigate the interactive effect of different spectral lights and CdO NPs on morphological, antioxidant, and phytochemical characteristics of Dodonaea viscosa. The plants were grown on media in the presence of green and chemically synthesized CdO NPs and under red, yellow, green, blue, and white light intensities. Results illustrated that plant morphological parameters changed in the presence of different spectral lights and NPs behaved differentially under different spectral lights. Fresh and dry weights of plants decreased in the presence of NPs in the media; however, the concentration and route of synthesis of NPs have a significant effect on these parameters. The same was observed in the case of shoot and root lengths; however, green synthesized NPs were found to be less toxic under different spectral lights. The total antixodant response increased under yellow, blue, and white lights, while the total reducing potential of plant extracts significantly varied depending upon the NP concentration and light spectrum. Different spectral lights significantly influenced the syntheses of phenolics and flavonoids under CdO NP stress and light regimes. It is concluded that toxicity of NPs also depends upon the wavelength of striking light that varies the morphological, biochemical, and antioxidative response of the plants. Furthermore, the white light might have synergistic effects of different wavelengths.