A solvothermal method has been used to produce nanoparticles of cubic/tetragonal yttria-stabilized zirconia (YSZ) with uniform particle size, homogenous composition, and high crystallinity. The effects of reaction time, reactant concentration, processing temperature, and solvent composition on prime particle size and YSZ phase proportion have been investigated. The effect of solvent, a mixture of ethanol/2-propanol, on crystallite size and agglomerate size was studied and discussed according to Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and surface chemistry. The prime particle diameter was 2-4 nm and secondary particle size was 140-180 nm. After compaction and sintering at 1000 degrees C, YSZ with a grain size of approximately 50 nm in diameter was obtained with a typical relative density of 94%.