Hollow Al2O3 spheres with ∼2 μm in diameter and ∼200 nm in wall thickness were prepared successfully via the calcination of the Al/AlOOH·nH2O core‐shell particles, prepared by wet‐chemical method using commercial microscale aluminum powders as raw materials, at 900°–1100°C in air. X‐ray powder diffraction, differential scanning calorimetric analysis, scanning electron microscopy, and transmission electron microscopy were used to characterize the obtained samples, and the possible formation mechanism was discussed. These hollow Al2O3 microspheres may have promising applications in insulators, lightweight fillers, and catalyst carriers because of their unique hollow structure.