This article presents a batch carbonation method with ultrasonication to synthesize monodispersed nanoparticles of calcium carbonate (CaCO3). The synthesis processes with and without ultrasonication were compared. The results showed that the application of ultrasonication into the synthesis caused a supersaturation Of Ca2+ ions in the synthesis, leading to a rapid nucleation of calcium carbonate and improved the solute transfer as well as. It was also found that the effect of ultrasonication on the grain size of the nanoparticles synthesized was related to other synthesis conditions, such as initial temperature for carbonation, mass fraction of Ca(OH)(2) suspension, and CO2 flow rate. The initial temperature applied for the carbonation was increased by at least 5 degrees C when ultrasonication was applied. The nanoparticles firmed in the presence of ultrasonication became smaller with a narrower particle size distribution at 6-12 wt.% of Ca(OH)(2) suspension or at 1.28 l/h of CO2 consumed by per gram of Ca(OH)(2) or more.