The surface state of vapor-phase-synthesized nonhydrated Al2O3 particles after milling was investigated quantitatively. The amount and kind of materials generated were different depending on the milling methods used and the ball grinding media. Gibbsite and bayerite were formed on the surface of Al2O3 particles in ball and planetary ball millings, respectively. On the other hand, wet-jet milling led to an undamaged Al2O3 particle surface as compared with other milling methods that use ball grinding media, in which the hydration reaction on the particle surface was also suppressed. In this work, the hydrodynamic interaction between Al2O3 particles in slurries prepared by various milling methods was investigated by rheological behavior characterization. From the creep and recovery measurements, it was found that the ball-milled and planetary ball-milled slurries behaved elastically. In the case of the wet-jet-milled slurry, the strain was proportional to the measurement time, indicating that the slurry had a liquid-like behavior. The creep compliance values of the ball-milled, planetary ball-milled, and wet-jet-milled slurries were 5.2 × 10−3, 1.5 × 10−3, and 14.8 × 103 Pa−1, respectively, indicating that the fluidity of planetary ball-milled slurry was lower than that of the ball-milled one. The fluidity of the wet-jet-milled slurry was fairly strong as compared with the ball-milled and planetary ball-milled ones. Moreover, the dynamic viscoelastic properties of the resulting slurries were measured at low strains in order to examine the rheology at long time scales. The behavior of the wet-jet-milled slurry in poly(acrylic acid) (PAA-NH4+) solution was similar to that of the PAA-NH4+-only solution. Therefore, it was found that the wet-jet-milled particles were more mobile in the slurry, with liquid-like behavior, and the attractive interaction between particles was very weak as compared with the ball-milled and planetary ball-milled ones.