The aim of this work was to investigate the influence of sintering temperature on the porous morphology, pore-size distribution, and apatite formation of sol–gel-derived porous bioactive glasses. For this purpose, three porous bioactive glasses were prepared by thermal phase separation cotemplate method in sol–gel process followed by sintering at 600°, 800°, and 1000°C. Pore structure of samples was characterized by various methods. The in vitro apatite formation test was carried out in simulated body fluid. The results showed that sintered bioactive glasses at 600°C exhibited a bimodal pore size distribution, mesopores, and nanopores (8–100 nm), macropores (100 nm–1 μm), and nanoscale pore walls (about 100 nm in width). The increase of sintering temperature induced the presence of a submicrometer pore-size distribution (300 nm–3 μm) with nanoscale pore walls (about 200 nm in width) and a morphological transformation from particle-like pore walls to dense pore walls. Depending on this porous structure, as-synthesized samples exhibited faster apatite formation capability.