To reveal the potential use of lactosylated-dendrimer (G3) conjugates with α-cyclodextrin (Lac-α-CDE (G3)) as novel hepatocyte-specific siRNA carriers in order to treat transthyretin (TTR)-related familial amyloidotic polyneuropathy (FAP), we evaluated the RNAi effect of siRNA complexes with Lac-α-CDE (G3) both in vitro and in vivo. Herein, we targeted TTR gene expression because TTR-related FAP was often caused by amyloidogenic TTR (ATTR), which mainly expresses in hepatocytes. Lac-α-CDE (G3, average degree of substitution of lactose (DSL) 1.2)/siRNA complex had a potent RNAi effect against TTR gene expression through adequate physicochemical properties, asialoglycoprotein receptor (ASGP-R)-mediated cellular uptake, efficient endosomal escape and the delivery of the siRNA complex to cytoplasm, but not nucleus, with negligible cytotoxicity. Lac-α-CDE (G3, DSL 1.2)/siRNA complex had the potential to induce the in vivo RNAi effect after intravenous administration in the liver of mice. The blood chemistry values in the α-CDE (G3) and Lac-α-CDE (G3, DSL 1.2) systems were almost equivalent to those in the control system (5% mannitol solution). Taken together, these results suggest that Lac-α-CDE (G3, DSL 1.2) has the potential for a novel hepatocyte-selective siRNA carrier in vitro and in vivo, and has a possibility as a therapeutic tool for FAP to the liver transplantation.