This research aims to investigate the effect of leucite particle size on the mechanical properties of dental porcelain with a similar leucite content and chemical composition. Leucite powders of different particle sizes were synthesized by a hydrothermal method and a high-temperature fusing-crystallization method, respectively. Dental porcelains with different average leucite particle sizes (i.e., 0.5 +/- 0.2, 1.2 +/-0.3, and 5 +/- 2 mu m) were prepared by sintering the mixture of different leucite powders and a low temperature frit. The crystalline phase, crystalline content, relative density, hardness, flexural strength, and fracture toughness of the porcelains were measured by X-ray diffraction (XRD), quantitative XRD analysis, the Archimedes method, a Vickers microhardness tester, a universal testing machine, and a single-edge precracked beam method, respectively. The microcrack density and the distribution of leucite particles were also quantitatively assessed from micrographs. The results showed that the leucite particle size did not have a significant effect on the average of the measured flexural strength, fracture toughness, and hardness of dental porcelains. However, because of a existence of the large number of microcracks, the relative density and the Weibull modulus of the sample groups with an average leucite particle size of 5 mu m were statistically lower.