A solid solution of 6H-type BaTi1-yCoyO3-δ samples where 0.1 ≤ y ≤ 0.4 and δ ≤ 0.05 has been prepared in air and characterized by a combination of X-ray, neutron, and electron diffraction, X-ray absorption spectroscopy, hydrogen-reduction thermogravimetric analysis, high resolution electron microscopy, magnetic susceptibility measurements, and impedance spectroscopy. For y = 0.1, Co acts as an acceptor dopant and is incorporated as CoIII ions with charge balanced achieved by the formation of O(2) oxygen vacancies in the h-BaO3 layers that separate pairs of face-sharing octahedra. For samples with y > 0.1, Co is present as both CoIII and CoIV ions and in all cases δ 0.03. This indicates a change from primarily aliovalent (CoIII) to isovalent (CoIV) doping with increasing Co-content with a general formula BaTiIV1-y(CoIII0.06CoIVy-0.06)O2.97 for 0.2 ≤ y ≤ 0.4. All samples are semiconducting at room temperature with relative permittivity in the range 20−50. The bulk conductivity increases with y and displays complex, non-Arrhenius-type behavior. All samples show paramagnetic behavior that can be fitted to the Curie−Weiss law from 150 to 300 K with a negative Weiss temperature indicating antiferromagnetic interactions between the magnetic Co ions. X-ray absorption spectroscopy data on a sample of y = 0.1 that retained the 6H-structure after heat treatment under reducing conditions revealed the existence of mixed state CoII and CoIII ions. A solid solution volume therefore exists for 6H−Ba(Ti,Co)O3-δ where the oxidation state of Co can vary from II to IV depending on the preparative conditions.