The objective of this work was to synthesize a sulfonated polymethylsiloxane (S-PMS) by hydrosilylation and sulfonation reactions and to investigate their effect on the growth of CaCO3 crystals using a gas diffusion method as a function of concentration, pH, and time. The result of IR and NMR shows good agreement with all proposed structures. Scanning electron microscopy images of CaCO3 showed small well-defined calcite-forming short piles (ca 5 mu m) and elongated calcite (ca 20 mu m) crystals. The morphology of the resultant CaCO3 crystals reflects the electrostatic interaction of sulfonate moieties and Ca2+ modulated by S-PMS adsorbed onto the CaCO3 surface. X-ray diffraction confirmed the crystalline calcite polymorph. Energy dispersive spectroscopy of CaCO3 crystals determined the presence of Si atoms from S-PMS. The use of PMS chemistry as an organic additive for the production of CaCO3 particles is a viable approach for studying the biomineralization and could be useful for the design of novel materials with desirable shape and properties.