Stimuli-responsive polymers have received considerable attention due to their ability to change properties in response to environmental changes. Polypeptoids are biocompatible and candidates for biomedical applications such as in controlled drug release and tissue engineering. In this work, we synthesized UV-sensitive diblock polypeptoids poly(sarcosine-r-butylglycine)-b-PNB (P(Sar-r-NBG)-b-PNB) and triblock polypeptoids polysarcosine-b-polybutylglycine-b-PNB (PSar-b-PNBG-b-PNB). Exposure to 254 nm UV light triggers the cleavage of nitrobenzyl groups leading to an increase in hydrophilicity, which is confirmed by UV/vis, H-1 NMR, and dynamic light scattering (DLS) analysis. Consequently, micelles formed by these block polypeptoids can undergo UV-trigged release of encapsulated cargo, herein exemplified using Nile red or pyrene as model payload. Furthermore, the diblock polypeptoids containing random P(Sar-r-NBG) segment exhibit thermoresponsive behavior, which is investigated by optical transmittance and DLS, and their cloud point temperatures (T(cp)s) can be adjusted by the feed molar ratio of Sar-NTA and NBG-NTA monomers. Furthermore, the block polypeptoids are able to self-assemble in water and show morphological changes from spherical nanoparticles to linear aggregates of several millimeters in length when the concentration increases. CCK-8 cell viability assays prove that the block polypeptoids' micellar aqueous solution is noncytotoxic before and after UV irradiation. Such novel biocompatible block polypeptoids with dual-responsive properties and varying morphology are of interest for applications in the field of biomedicine.