Hierarchical urchin-like γ-Al₂O₃ hollow microspheres were prepared by a hydrothermal method followed by a calcination process using Al(NO₃)₃·9H₂O as aluminum source, NH₃·H₂O as precipitating agent, and P123 as structure-directing agent (SDA). The obtained samples were investigated using X-ray diffraction (XRD), filed emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and N₂ adsorption/desorption. The influences of P123 concentration, acidic condition, and hydrothermal time on the morphology of product were discussed. P123 has a great influence on ruling the oriented attachment of nanowires and stabilizing the superstructure in the self-assembly process. The 3D urchin-like hollow microspheres have a surface area of 210.2 m²/g and the average pore size is 11.42 nm, which have widely potential application such as catalyst, adsorption, and separation.