Hierarchically porous In2O3/In2S3 heterostructures with micro-meso-macropores were prepared via a novel polymer-assisted sol-gel freeze-drying route, combined with self-sacrificial sulfidation processing. The three-dimensional hierarchical porous structure (3DHPS) In2O3/In2S3 showed outstanding photocatalytic activity, and the photocatalytic rate constant (k) of the 3DHPS In2O3/In2S3 was 3.7 times larger than that of In2O3/In2S3 nanoparticles. Such efficient photocatalytic ability could be mainly ascribed to the following aspects: first, the formation of In2O3/In2S3 heterostructures inhibited the recombination of the photogenerated carriers; second, the hierarchically porous structure, acting as micronano reactors, could offer high surface area and numerous reactive sites; third, the 3D open scaffolds could increase the light harvesting and facilitate mass transport of reactants. Moreover, due to their self-supported structures, the 3DHPS In2O3/In2S3 did not need to be separated for reuse. The micronano reactor-like In2O3/In2S3 heterostructures with excellent photocatalytic activity and favorable recycling properties exhibit great potential in environmental remediation and green energy production.