Highly stable hybrid unimolecular micelles with thermosensitive poly(N-isopropylacrylamide) ( PNIPAM) shells incorporated with Ag nanoparticles were prepared in situ via a facile approach. Heating the hybrid unimolecular micellar solutions leads to the shrinkage of the PNIPAM shell and allows for tuning the relative spatial distances between neighboring Ag nanoparticles. Because of the anchoring and stabilization of PNIPAM brush to the Ag nanoparticles, the tuning of spatial distribution of nanoparticles within the unimolecular micelles is completely reversible with heating/cooling cycles. The facile preparation procedures and their efficiency of response to the surrounding media render these novel hybrid unimolecular micelles potential candidates for applications in sensors, catalysis, and optic/electronic devices.