An amphiphilic, Janus diblock hyperbranched copolyamide was synthesized by the condensation of hydroxyl and carboxyl groups at the focal point of hydrophilic and hydrophobic hyperbranched polyamides, respectively, in the presence of a condensation agent. The structure of the self-assembled Janus diblock hyperbranched copolyamide in water at 25 °C, observed by using a transmission electron microscope, consisted of spherical aggregates. As the temperature of the solution was increased, the morphology changed to cylindrical-like aggregates at 50 °C and to dendritic-like aggregates at 70 °C. An amphiphilic, Janus diblock hyperbranched copolyamide was synthesized by the condensation reaction, and the morphologies of aggregates in water were changed from spherical to dendritic-like structures via cylindrical-like structures in response to increasing temperature.