The composites of Cu-partially substituted bismuth vanadate (BICUVOX.1) mixed with a small amount of partially stabilized zirconia (3Y-TZP) were prepared to investigate their microstructure, mechanical properties and ionic conductivity. It was found that the addition of 0.5 to 1 wt% 3Y-TZP reduces the grain size to lower than 1 mum in diameter, leading to improvements in micro-hardness and toughness by more than 15%. Due to preferential distribution of 3Y-TZP particles along grain boundaries, grain boundary conductivity and total conductivity decreased with increasing 3Y-TZP content at low temperature, but the decrements remained rather modest and, in addition, became less significant at higher temperature to disappear at 700 K and above.