Fe3O4-SnO2 composite has been prepared by hydrothermal and sonochemical methods. The electron microscopic images confirm the prepared composites as nanomaterials. The X-ray diffractograms show tetragonal SnO2 and cubic Fe3O4 as the components of the prepared nanocomposites. The energy-dispersive X-ray spectra provide the composition of hydrothermally prepared composite as 62% (mol.) SnO2 and 38% (mol.) Fe3O4 and the composition of sonochemically obtained composite is 12% (mol.) SnO2 and 88% (mol.) Fe3O4. Both the composites absorb visible light. The composites are superparamagnetic, and the saturation magnetization of hydrothermally prepared nanocomposite is less than that of sonochemically obtained one. The visible light-photocatalytic activity of hydrothermally prepared nanocomposite is larger than that of the other. In addition, both the nanocomposites exhibit bactericidal activity. As the hydrothermally prepared nanocomposite is a magnetically recoverable bactericidal visible light-photocatalyst, it is a promising candidate for environmental cleanup. (C) 2013 Elsevier B.V. All rights reserved.