In this work, an analysis was made of the microstructural effects derived from the incorporation of silver (Ag) at different concentrations (0.5, 1, 2, 3, and 8% wt) to obtain ZnO-Ag nanocomposites. The results show an increase in the particle size of Ag in relation to the increase in the weight percentage of the precursor. ZnO-Ag is obtained through an infusion of Origanum vulgare as a reducing agent for Ag in the first stage. Subsequently, the solid-state method was used, resulting in the formation of Zinc Oxide (ZnO) and the ZnO-Ag nanoparticles (NPs). The physicochemical characterization was carried out using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and High-Resolution Transmission Electron Microscopy (HRTEM). The XRD results confirm the presence of Ag and ZnO. Ag shows a preferred orientation of [111] with a crystallite size ranging from 28.46 to 44.92 nm, which increases with the percentage of Ag in the system over ZnO. The wurtzite ZnO presents a preferential orientation of [101] with an increasing crystallite size from 24.9 to 29.84 nm. In the FTIR analysis, a stretching band at 682 cm⁻¹, characteristic of the Zn-O bond, as well as a strain vibration band at 457 cm⁻¹ of ZnO, were observed. The nanoparticle size is attributed to the phytochemical composition of Origanum vulgare, which includes secondary metabolites such as phenolic acids, flavonoids, terpenoids, and flavonoid-based reducing compounds. These compounds help reduce the agglomeration of the particles.