A method for preparing multiphasic hollow rods consisting of nanoscale Sn-based materials through a thermochemical reduction process involving bacteria and Sn oxides is reported. This facile process involves the bacteria-mediated synthesis of SnO₂ nanoparticles that form on bacterial surfaces used as templates at room temperature. The subsequent template removal proceeds via a reduction of the heat-treated SnO₂ nanoparticles at 400 °C under reduction atmosphere, leaving free-standing hollow nanocomposite rods. These unique hollow nanocomposite rods have multiple components, including amorphous carbon, metal oxides (SnO₂ and SnO), and metallic Sn, and retain the original rod shapes. The systematic phase and morphological evolutions of the bacteria@SnO₂ composite rods are investigated by performing controlled thermochemical reduction at various temperatures. In addition, the application of multiphasic hollow nanocomposite rods as anode materials for rechargeable Li-ion batteries is evaluated. These materials exhibit excellent electrochemical performance, with capacities of about 505 and 350 mA h g⁻¹ at current densities of 157 and 392 mA g⁻¹, respectively.