Facile synthesis of hydrophobic calcium carbonate (CaCO₃) had been conducted via aqueous reaction route incorporated with stearic acid. Ammonium stearate (C₁₇H₃₅COONH₄) solution prepared from stearic acid (C₁₇H₃₅COOH) and ammonium hydroxide (NH₄OH) was used as substrate for modifying surface property of the synthesized CaCO₃, resulting in not only the nucleation and growth of CaCO₃ particles but also formation of hydrophobic surface of CaCO₃. The optimal initial calcium hydroxide Ca(OH)₂ concentration which providedunique particles size and morphology was 2 mM with 49% yield.The carbonation temperature was animportantfactorto regulate the formation of aragonite morphology. Needle-like aragonite was precipitated at 60 and 90 °C. However, the incubation temperature was a minor influence for precipitated CaCO₃ particles. In addition, morphology, crystallinity and functional groups on surface of CaCO₃ were characterized by scanning electron microscopy, X-ray diffraction spectroscopy and Fourier Transform Infrared spectroscopy. Image processing program was employed for examining linkages of particle physical characteristics and the synthesizing conditions. As a result, it could be implied that usage of stearic acid withcontrolof carbonation temperature would be essential for synthesizing nano-scalled CaCO₃ with hydrophobic property.