Stable hollow ZrO₂–SiO₂ spheres with mesopores in the shell wall have been successfully synthesized by a sol–gel process in an oil–water–oil microemulsion. The samples were characterized by transmission polarized light microscopy, SEM, TEM, and N₂ adsorption–desorption isotherms. The characterization results indicate that a large number of mesopores are present in the shell wall of the calcined hollow ZrO₂–SiO₂ spheres, and that the diameter and shell thickness are ca. 50 and 15 µm, respectively. The hollow spheres exhibit high thermal stability and remain intact spherical structures even after calcination at 550 °C for 8 h. In the cracking reactions of cumene and 1,3,5-triisopropylbenzene the sulfated hollow ZrO₂–SiO₂ spheres show very high catalytic activities. Especially, the higher catalytic activity of 1,3,5-triisopropylbenzene cracking suggests the potential application in cracking of bulky molecules. A possible formation mechanism of hollow spheres of binary composite oxide is also proposed.