s-Triazine-based hyperbranched polyurethanes (HBPUs) with different hard segments were synthesized by A(2) + B-3 approach. Various kinds of multiwalled carbon nanotube (MWNT) nanocomposites with HBPU were prepared to investigate an impact of hyperbranched polymer on dispersion of MWNTs in the polymer matrix and the resulting properties of nanocomposites. Synthesized HBPUs were characterized using FTIR and NMR measurements. The highly branched structures were found very effective in enhancing the pristine MWNT dispersion in the polymer matrix. As a result, the MWNT-reinforced HBPU nanocomposites showed a steep increase in the yield stress and modulus and enhanced shape memory effect with an increase of hard segment and MWNT loading. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 474-483, 2011