We successfully obtained silicate-mediated CaCO3 films on a chitosan surface in an aqueous solution system. The presence of silicate anions induced the miniaturization of the carbonate crystals and two-dimensional growth with the arrangement of the miniaturized subunits on the functional surface. The mortar-like effects of silicate anions on the morphological evolution were quite similar to those of organic polyelectrolytes having carboxy groups, such as poly(acrylic acid).