A novel terminal modification agent to endow hyperbranched polyamidoamine (HPAMAM) with thermo-/pH-responsive properties is reported. HPAMAM with terminal vinyl groups is first synthesized and then end-capped by 1-adamantylamine (ADA). The resulting hyperbranched polymer (HPAMAM-ADA) shows interesting thermo-responsive properties in aqueous solution, which have been investigated by UV-vis spectroscopy, optical microscopy, and ¹H NMR spectroscopy. The lower critical solution temperature can be controlled by adjusting the end-capping ratio of ADA. In addition, HPAMAM-ADA exhibits a pH-dependent water solubility. This pH-responsive behavior is also studied.