Abstract <p>Visible-light-driven 0–5 wt % In-doped ZnO nanoparticles were synthesized by precipitation method using tartaric acid as a chelating complex. The TGA revealed that the precursors were completely transformed into crystalline ZnO and In-doped ZnO above 580°C. XRD patterns of ZnO with and without In dopant were indexed to be pure hexagonal wurtzite ZnO structure. The TEM images revealed that ZnO with and without In dopant were composed of nanoparticles with different orientations. Their crystallite sizes were decreased with increasing in the content of In dopant. The XPS analysis confirmed that In³⁺ ions were incorporated in ZnO lattice. The photocatalytic activities of ZnO nanoparticles doped with different contents of In dopant were tested for photocatalysis of methylene blue (MB) under visible radiation. The 3 wt % In-doped ZnO nanoparticles have the highest activity in degrading MB dye and are the promising photocatalyst used for wastewater treatment.</p>