Electrophoretic deposition (EPD) of yttria-stabilized zirconia (YSZ) particles on metal substrates has been examined as a function of EPD conditions and suspension properties. The packing density of particles, i.e., volume occupation of particles in a wet deposit, depends on the deposition time, applied voltage, and the electrical conductivity and solid concentration of the suspension. In addition, the packing density of particles in a wet deposit further increased when the deposit was immersed in a pure acetylacetone solvent with application of a constant electric field. The packing mechanism of YSZ particles in the wet deposit was discussed based on the electro-osmotic flow mechanism of YSZ particles during EPD.