Hydrothermal synthesis of nano ZrO2 powders were carried out at a temperature range of 100 to 200°C, using zirconium solution. Formation of ZrO2 formation was accelerated with temperature and precipitation of ZrO2 took place directly from the solution. XRD analysis revealed that monoclinic ZrO2 was formed at all conditions. Crystallite size was found to range from 2.6 to 4 nm. Mean particle size increased from 93 nm at 135°C to 125 nm at 200°C after reaction time of 2 h.