Nano-sized calcium carbonate (nano-CaCO3)-supported nucleating agent for poly(L-lactide) (PLLA) was prepared by supporting calcium phenylphosphonate (PPCa) on nano-CaCO3 surface. The thermal properties of phenylphosphonic acid (PPOA) and nano-CaCO3-supported nucleating agent and its dispersion in PLLA matrix were investigated by differential scanning calorimetry and field emission scanning electron microscopy. The results indicated that the formation of nucleating agent supported on nano-CaCO3 was attributed to the chemical reaction between nano-CaCO3 and PPOA. The nano-CaCO3-supported nucleating agents were dispersed evenly in the PLLA matrix even with 5 wt% loading. The supported nucleating agent was added to PLLA to examine its nucleating ability for PLLA. The results of the investigation showed that the nano-CaCO3-supported nucleating agent exhibited higher nucleation ability compared to PPCa nucleating agent. POLYM. ENG. SCI., 2012. (C) 2012 Society of Plastics Engineers