To mediate selective gene delivery to hepatocytes via the asialoglycoprotein receptors (ASGP-Rs), we designed and synthesized well-defined and narrowly dispersed galactose- and glucose-functionalized cationic polycarbonate diblock copolymers (designated as Gal-APC and Glu-APC, respectively) using organocatalytic ring-opening polymerization of functionalized carbonate monomers, with a subsequent quaternization step using bis-tertiary amines to confer quaternary and tertiary amines for DNA binding and endosomal buffering, respectively. The sugar-functionalized diblock copolymers effectively bound and condensed DNA to form positively charged nanoparticles (<100 nm in diameter and approximate to 30 mV zeta-potential) that were stable under high physiological salt conditions. In comparison to the control Glu-APC/DNA complexes, Gal-APC/DNA complexes mediated significantly higher gene expression in ASGP-R positive HepG2 cells with no significant difference observed in ASGP-R negative HeLa cells. The co-incubation of Gal-APC/DNA complexes with a natural ASGP-R ligand effectively led to a decrease in gene expression, hence providing evidence for the ASGP-R mediated endocytosis of the polyplexes. Importantly, the Gal-APC/DNA complexes induced minimal cytotoxicities in HepG2 cells at the N/P ratios tested. Taken together, the galactose-functionalized cationic polycarbonate diblock copolymer has potential for use as a non-viral gene vector for the targeted delivery of therapeutic genes to hepatocytes in the treatment of liver diseases.