This study describes a novel thermoresponsive dendritic polyethylene glycol-poly(D, L-lactide) (PEG-PDLLA) core-shell nanoparticle with potential for drug delivery and controlled release. Dendritic PEG-PDLLA in aqueous phase could self-assemble into spherical aggregates and the size of spherical aggregates increased with PEG chain length increase. Further, spherical aggregates made of dendritic PEG-PDLLA exhibited magnified temperature- dependence in terms of solubility change and dimension expansion as compared to linear PEG-PDLLA. The most significant size expansion was observed in particles made of dendritic PEG (12000)-PDLLA, which was twice as much as that of particles made of linear PEG (12000)-PDLLA. Water insoluble antitumor drug camptothecin (CPT) was used as a model drug for encapsulation and release studies. Spherical aggregates encapsulated more CPT when dendritic PEG-PDLLA had longer PEG-PDLLA chain and/or when temperature was elevated to body temperature. This study demonstrated that nanoscale clustering PEG-PDLLA through dendrimers magnified the thermo-sensitivity of PEG-PELLA. Successful development of such a new particulate system made of dendritic PEG-PDLLA with an expandable dimension in response to temperature change generated a new direction for designing stimuli-responsive materials.