Monodisperse closed-pore silica spheres with small pore diameters have been prepared through a simple self-assembly approach. The closed-pore silica spheres were synthesized in near neutral conditions, using cetyltrimethyl ammonium bromide (C₁₆TAB) as a template. The products show a spherical morphology with a uniform size of 120 nm in diameter, which are formed by the dense packing of silica coated spherical micelles with 5 nm in diameter and 3 nm in isolated interior space. It is shown that the use of a cationic surfactant and synthetic conditions that stabilize the silica coated spherical micelles are responsible for the formation of a closed-pore mesostructure. Considering the silica-coated micelles, the building blocks to the closed-pore mesostructure, have a smaller size compared to those in previous reports, it is expected that our approach may be extended to prepare functionalized materials with potential applications as low dielectric constant insulators in the microelectronics industry.