Barium titanate (BaTiO3) nanopowders were prepared through a combined polymerization and pyrolysis of a metallo-organic precursor. The mean particle size d(m) could be adjusted by choosing appropriate reaction temperatures and tempering atmospheres. In the present in situ study of this particular solid-phase reaction, X-ray absorption near-edge structure (XANES) spectroscopy at the Ti K and Ba L-3 edges was applied in the preparation route of BaTiO3 nanopowders. A pronounced distortion of the lattice symmetry was found to occur in very fine BaTiO3 nanopowders (d(m) < 20 nm). These findings are in apparent contradiction to recently reported XANES data, which, however, refer to coarser BaTiO3 nanopowder samples (d(m) > 20 nm). In addition, Ti K XANES investigations were performed in the formation of titanium dioxide (TiO2) nanopowders as a reference case, enabling identification of amorphous TiO2 as an intermediate in the BaTiO3 preparation route.