Normal maize starch samples with moisture contents of 11.24, 6.18, and 1.5% were ground using a fluidized bed jet mill at classifier frequencies of 2400, 3000, 3600, and 4200 to produce micronized starch powder. The changes in structural and functional properties of the starch after jet milling process were studied. The particle size of starch significantly (p < 0.05) decreased after jet milling and as the classifier frequency increased. Also, the bulk and tap density decreased; while the specific surface area increased and the flowability of the milled samples became quite poor as the classifier frequency increased. The microscopy analysis showed that the jet milling destroyed the crystalline areas and promoted amorphous areas of starch granules. The micronized starch samples showed significant (p < 0.05) increase in the water solubility, swelling power, water and fat holding capacities, and pasting temperature compared with the native starch. However, a decrease in viscosity parameters of starch was found after jet milling and as classifier frequency increased. The initial moisture content of starch showed a slight effect on the functional properties of the micronized starch. The obtained results suggest that modified starch can be produced by fluidized bed jet milling.