An environmentally friendly technique was used to prepare titanium dioxide@ silver (core shell) (TiO₂@Ag NPs) using chard leaf extract, a natural stabilizer and reductant. A nanocomposite (NCs) of TiO₂@Ag supported by halloysite nanotubes (HNTs), TiO2@Ag/HNT NCs, was prepared under microwave irradiation. The microwave technique is used to accelerate the reaction and enhance the homogeneity of nanoparticle distribution. Spectroscopic and structural analyses were performed on the resulting nanocomposite. X-ray diffraction (XRD) revealed a clear crystalline structure with grain sizes ranging from 7 to 15 nm, with an average of ~11 nm, the transmission electron microscope (TEM) revealed that the size of nanoparticles in the TiO₂@Ag/HNT NCs sample ranges from 20 to 80 nm, with some localized agglomerations visible in specific areas. UV–Vis absorption spectra indicated significant optical activity in the visible and UV ranges, indicating improved photonic properties. Fourier transform infrared (FTIR) spectra revealed the presence of intergroup bonds. The active ingredients in the plant extract and the TiO2@Ag/HNT nanocomposite surface were found, indicating the extract’s role in stabilization. The zeta potential test showed good stability, with a value of −57 mV. The TiO₂@Ag/HNT NCs demonstrated high efficiency in the adsorption of heavy metal mercury (Hg(II)) from contaminated water, achieving a removal rate of 100%. This result reflects the unique effectiveness of the TiO₂@Ag/HNT and its outstanding ability to treat mercury pollution efficiently. These results demonstrate the potential for producing a multifunctional nanocomposite in an environmentally friendly and efficient manner, making it a practical option for various photocatalytic and water treatment applications.