During this paper, the Ag/HZSM-5 nanocomposite has been successfully synthesized by using an aqueous extract of Euphorbia heterophylla leaves as a stabilizing and reducing agent. The green synthesized Ag/HZSM-5 nanocomposite was characterized by FT-IR (Fourier transform infrared spectroscopy), FESEM (field emission scanning electron microscopy), EDS (energy dispersion X-ray spectroscopy), UV–vis, XRD (X-ray powder diffraction) and elemental mapping. The Ag/HZSM-5 nanocomposite was found to be efficient nanocatalyst for the reduction of organic dyes such as Methylene blue (MB), Congo red (CR), Rhodamine B (RhB) and 4-nitrophenol (4-NP) in water at room temperature. The catalytic activities of the nanocatalyst in reactions were monitored by using UV–vis spectroscopy. Interestingly, the Ag/HZSM-5 catalyst can be easily recovered and reused several times without any significant loss of catalytic efficiency.