The growth of mesoporous quasi-single-crystalline Co3O4 nanobelts by topotactic chemical transformation from α-Co(OH)2 nanobelts is realized. During the topotactic transformation process, the primary α-Co(OH)2 nanobelt frameworks can be preserved. The phases, crystal structures, morphologies, and growth behavior of both the precursory and resultant products are characterized by powder X-ray diffraction (XRD), electron microscopy—scanning electron (SEM) and transmission electron (TEM) microscopy, and selected area electron diffraction (SAED). Detailed investigation of the formation mechanism of the porous Co3O4 nanobelts indicates topotactic nucleation and oriented growth of textured spinel Co3O4 nanowalls (nanoparticles) inside the nanobelts. Co3O4 nanocrystals prefer  epitaxial growth direction of hexagonal α-Co(OH)2 nanobelts due to the structural matching of  α-Co(OH)2// Co3O4. The surface-areas and pore sizes of the spinel Co3O4 products can be tuned through heat treatment of α-Co(OH)2 precursors at different temperatures. The galvanostatic cycling measurement of the Co3O4 products indicates that their charge–discharge performance can be optimized. In the voltage range of 0.0–3.0 V versus Li+/Li at 40 mA g−1, reversible capacities of a sample consisting of mesoporous quasi-single-crystalline Co3O4 nanobelts can reach up to 1400 mA h g−1, much larger than the theoretical capacity of bulk Co3O4 (892 mA h g−1).