A series of highly branched waterborne poly(urethane-urea)s (HBWPUs) containing pendant carboxylate anion as the hydrophilic groups were prepared via A(2) + B-3 approach using isocyanate end-capped poly-carbonatediols as an A(2) oligomeric monomer and triamine as a B-3 monomer. The structure of the products were characterized by FTIR and C-13-NMR. The particle size, solution viscosity, thermal and mechanical properties were measured by photon correlation spectroscopy (PCS), rotational rheometer, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA) and tensile tests, respectively. It was found that the particles size mainly depended on the molar ratio of nNCO/nOH and the content of hydrophilic groups; the HBWPUs showed lower viscosity but higher T-g compared with linear waterborne polyurethane. The tensile testing, DMA measurements and rehological measurements revealed that the molar ratio of [B-3]/[A(2)] had significant influence on the viscosity and tensile strength. With increasing the molar ratio of [B-3]/[A(2)], both the viscosity and the tensile strength decreased. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 817-824, 2010