Hierarchical Fe3O4@polypyrrole nanocages constructed with thin nanosheets are synthesized via a reduction and in situ polymerization route. They exhibit a stable cycling performance (650 mA h g−1 capacity at 2000 mA g−1 after 500 cycles) and superior rate capability (reversible capabilities of 1120, 950, 796, 657, and 490 mA h g−1 at 100, 300, 1000, 2500, and 5000 mA g−1, respectively).