The electrical conductivity of BaTh0.9Nd0.1O3-alpha is about four times larger than that of BaCe0.9Nd0.1O3-alpha around 1273 K in dry air, and increases in proportion to P(O2)1/4.3 at 1263 K in a dry atmosphere, suggesting p-type electronic conduction. The contribution of oxide ionic conduction increases with decreasing temperature and the activation energy of oxide ionic conduction is about 0.46 eV. The water vapor pressure dependence of the total electrical conductivity suggests that conduction in BaTh0.9Nd0.1O3-alpha is protonic.