Whiskers of mesostructured silicate having a sharp top and hexagonal habits were formed on a flat substrate by surfactant-templated synthesis in an acidic solution system. In the initial stage of whisker formation, truncated cones of hexagonal mesosilicate covered the surface through heterogeneous nucleation. Whisker structures were constructed on the truncated cones by surfactant micelles accompanied with silicate through a hexagonal plan. The formation of sharp whiskers is ascribed to instability of the surface of the mesostructured silicate-surfactant composite in a diffusion field.