A new amphiphilic Y-shaped copolymer, comprised of hydrophobic poly(undecylenic acid) (PUA) and hydrophilic poly(N-isopropylacrylamide) (PNIPAAm), was designed and synthesized. A cytotoxicity study revealed that P(UA-Y-NIPAAm) copolymers did not exhibit apparent inhibition impact on the proliferation of cells when the concentration of the copolymer was below 1000 mg/L. Characterization demonstrated that the P(UA-Y-NIPAAm) copolymer is thermosensitive with a lower critical solution temperature (LCST) of 31 degrees C. In water, the P(UA-Y-NIPAAm) copolymer would self-assemble into micelles with a critical micelle concentration (CMC) of 20 mg/L. Self-assembled P(UA-Y-NIPAAm) micelles exhibited a nanospherical morphology of 40 to similar to 80 nm in size. The controlled drug release behavior of the P(UA-Y-NIPAAm) micelles was further investigated, and self-assembled micelles exhibited improved properties in controlled drug release.