This study systematically investigates the structural, optical, and photocatalytic properties of Zn1−xAgxO nanoparticles (0.00 ≤ x ≤ 0.04) synthesized through an energy-efficient co-precipitation method at 60 °C. Comprehensive characteriza tion using XRD with Rietveld refinement confirms the successful incorporation of Ag+ ions into the ZnO lattice while maintaining its hexagonal wurtzite structure, with crystallite sizes decreasing from 71.06 nm (undoped) to 37.67 nm (x = 0.04). Optical analysis reveals a controlled bandgap reduction from 3.00 eV to 2.75 eV with increasing Ag content, significantly enhancing visible light absorption. The optimized Ag-ZnO photocatalyst demonstrates exceptional perfor mance with 89.8% methylene blue degradation under UV irradiation. These findings highlight the material’s potential for industrial wastewater treatment applications, while also identifying the need for further bandgap engineering to improve sunlight-driven photocatalytic activity through co-doping strategies or heterojunction formation.