In this work, Au/Fe₃O₄ nanocomposite materials with exact spinel structure were successfully synthesized where impurities-free Fe₃O₄ was prepared using sol–gel auto-combustion method and gold was doped with various concentrations 1, 3, and 5 wt.% using conventional deposition–precipitation method. Methylene blue with fixed concentration (0.05 mM) was used to investigate the photocatalytic activity under visible light. Due to homogeneous and controlled compositions, Au/Fe₃O₄ nanocomposites showed enhanced photocatalytic efficiency than pure Fe₃O₄.