Maize starch–water suspensions (1.0%) were subjected to single-pass high-pressure homogenization treatment at 60 MPa, 100 MPa, and 140 MPa. The structure and thermal properties of the high-pressure homogenized starches were investigated using DSC, X-ray diffraction technique, laser scattering, and microscope, with native maize starch (suspended in water, but not homogenized) as a control sample. DSC analysis showed a decrease in gelatinization temperatures (To,Tp) and gelatinization enthalpy (DHgel) with increasing homogenizing pressure. No noticeable effect of high-pressure homogenization on the retrogradation of maize starch was observed. Laser scattering measurements of particle size demonstrated an increase in the granule size at a homogenizing pressure of 140 MPa. This was attributed to the gelatinization and aggregation of the starch granules. X-ray diffraction patterns showed that there was an evident loss of crystallinity after homogenization at 140 MPa. Microscopy studies showed that the maize starch was partly gelatinized after high-pressure homogenization, and the gelatinized granules were prone to aggregate with each other, resulting in an increase of granule size.