Macromolecular self-assembly is attracting increasing scientific interest in polymer science. One of the most studied assemblies are stimuli-responsive polymersomes that can convert specific environmental changes to functional outputs based on a physicochemical adjustment of their chain structures and membrane properties. These unique features have made it possible to design and construct smart self-assembled architectures for various emerging applications such as polymeric nanocapsules for tunable delivery vehicles. Moreover, stimuli-responsive polymersomes possess the ability to encapsulate active enzymatic species which makes them well suited as nanoreactors capable of performing enzymatic reactions. In this regard, this class of smart polymersomes provides an avenue to apply synthetic polymer systems as biomimetic materials. Here, in this review, we will highlight recent progress with regard to stimuli-responsive polymer vesicles/nanocapsules and their development towards intelligent nanocarriers and nanoreactors or artificial organelles.