In3Se4 and S-doped In3Se4 nano/micro-structures consisting of thin nanosheets have been developed as new anode materials for Li-ion batteries. Electrochemical performance measurement shows that In3Se4 nano/micro-structures deliver high discharge capacity (e.g. 651.0 mA h g-1 obtained in the 30th cycle at a current density of 50 mA g-1). Through detailed transmission electron microscopy analysis, it has been found that the electrochemical reaction mechanism is the conversion between In3Se4 and Li13In3 + LixSe. Moreover, S doping is demonstrated to be an effective approach to further improve the electrochemical performance of In3Se4 nano/micro-structures. S-doped In3Se4 nano/micro-structures achieve enhanced discharge capacity and cycling stability, with a discharge capacity of 850.6 mA h g-1 in the 30th cycle. This study demonstrates the potential of In3Se4-based nano/micro-structures as anode materials for rechargeable Li-ion batteries.