The effect of Al2O3 addition on sinterability of Tetragonal Zirconia Polycrystal powders including 3mol% Y2O3 (3Y-TZP) was investigated. Each 3Y-TZP powder dispersed with 0.3, 0.6, 0.9 and 1.2wt.% of Al2O3 was prepared by the spray-drying method. The prepared powders were pressed into a disk type and sintered at 1350, 1400, 1450 and 1500 for 2 hours in the air. Resultant microstructures and mechanical properties of specimens were investigated by using Vickers/Micro hardness Tester, FE-SEM and XRD. Most of the specimens showed high relative density over 99% and a higher fracture toughness than pure 3Y-TZP. Al2O3 particles dispersed in 3Y-TZP microstructure depressed grain growth of 3Y-TZP by the pinning effect. Increase in fracture toughness of 3Y-TZP was explained by the crack deflection due to dispersed Al2O3 particles.