A solid solution forms for Sr3NdNb3-xTixO12-d with approximate limits 0 ≤ x ≤ 0.06. The system crystallizes with a 12R-type hexagonal perovskite structure in space group , as determined by neutron diffraction and selected area electron diffraction. The electrical properties of the end members have been investigated by impedance spectroscopy in the temperature range 550 -800 °C in various gas atmospheres and as a function of oxygen and water-vapour partial pressure. Proton transport dominates in wet oxidising conditions in the temperature range 550 to 700 °C, as confirmed by the H+/D+ isotope effect. Acceptor doping considerably enhances proton conductivity with a value of 3.3 × 10-6 Scm-1 for the bulk response of x = 0.06 at 700 °C in moistened air. The presence of a - ¼ slope for both doped and undoped samples in the range 10-19 ≤ pO2 ≤ 10-8 atm at 900 °C indicates n-type transport in reducing conditions following the extrinsic model attributable to acceptor centres. The conductivity is essentially independent of pO2 at 600 °C in dry oxidising conditions, consistent with oxide-ion transport; a positive power-law dependence at higher temperature indicates extrinsic behaviour and a significant electron-hole contribution. The dielectric constant at RT of nominally stoichiometric Sr3NdNb3O12 is εr ~ 37, with a moderately high quality factor of Q × f ~ 16400 GHz at fr ~ 6.4 GHz. The temperature coefficient of resonant frequency of x = 0 is τf ~ 12ppm/°C, which lowers to -3 ppm/°C for the Ti-doped phase x = 0.06.