The persistent presence of organic dyes poses a significant contemporary challenge, prompting scientific efforts to develop materials capable of mitigating their harmful effects on our primary life source, water. Here, we report the biosynthesis of copper-embedded silica (CuO@SiO2) nanocomposite using an aqueous leaf extract of the Barleria prionitis L. plant, alongside the synthesis of copper oxide (CuO) and silicon dioxide (SiO2) nanoparticles employing a similar method. Characterization via UV-Vis. spectroscopy and FTIR spectroscopy confirmed the formation of nanocomposites and nanoparticles, elucidating the presence of hydroxyl (−OH) and carbonyl (−C=O) groups inherent in the phytochemicals of the plant extract. Characterization methods like X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) have been used for the structural and morphological investigation of nanocomposites. Biological activities, such as testing for antioxidants, have also been carried out. Comprehensive biological assessments are essential for determining biocompatibility, cytotoxicity, antibacterial efficaciousness, therapeutic potential, and environmental impact for safe and efficient use of nanocomposites. Subsequently, the biosynthesized CuO@SiO2 nanocomposite exhibited remarkable catalytic properties when employed as a photocatalyst for the degradation of organic dyes, methyl orange (MO), and crystal violet (CV), particularly demonstrating enhanced performance under visible light irradiation. Furthermore, the utilization of plant extract is anticipated to confer additional biological properties, such as antimicrobial and antioxidant activity, to the resulting composite material.