Highly mesoporous antimony-doped tin oxide (ATO) materials with three-dimensionally connected textural pores were prepared by a convenient one-pot process by creating, drying and calcining hydrous ATO and resorcinol–formaldehyde composite gels. The synthesis is designed to form a hydrous ATO gel structure first at room temperature and upon subsequent heating at 70 °C the inorganic gel network catalyzes the full polymerization of resorcinol and formaldehyde. The resulting polymer network interpenetrates the inorganic gel network and serves as a hard template during drying and calcination. The final products show a good crystallinity and have high surface areas up to 100 m² g⁻¹ and high porosities up to 69%. The average pore sizes range from 7 to 33 nm, controlled mainly by varying the amount of the polymer component in the composite gels. The materials exhibit remarkably low resistivities (>0.14 Ω cm) for a mesoporous ATO material.