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Purpose: This study analyzed the mechanical properties of dental zirconia blocks as a function of the size of artificially introduced initial cracks. Methods: Rectangular specimens (30×4×3 mm) were prepared, and cracks were introduced using a Vickers hardness tester under 0 (no applied load), 5, 20, and 30 kg loads. The crack lengths and indentations were measured microscopically, and the fracture toughness was calculated. Results: The Vickers hardness ranged from 1,414.9 to 1,515.5 kgf/mm2, and the fracture toughness ranged from 5.2 to 8.2 MPaㆍm1/2. The higher the load, the larger the cracks created. Further, the bending strength of zirconia decreased considerably as the cracks propagated. Uncracked specimens had a strength of 1,147~1,244 MPa, whereas cracked specimens with 5, 20, and 30 kg loads exhibited values of 237~290, 179~191, and 140~152 MPa, respectively. The fatigue life also reduced drastically with the crack appearance, falling to ≤1,060 cycles, compared with the over 1 million cycles observed for the intact specimens. Conclusion: Initial cracks considerably decreased the bending strength and fatigue life of zirconia. The size of the initial cracks increased with the indentation load, resulting in a decrease in the bending strength and fatigue life.