In this work, we present the chain exchange kinetics in block copolymer micelles of spherical and cylindrical geometry. The aim of this work was to understand the mechanisms controlling the molecular exchange with a particular focus to delineate any potential effect of the micellar morphology. As model system symmetric short-chain amphiphilic poly(ethylene-alt-propylene)-poly(ethylene oxide) diblock copolymer (PEP1–PEO1, numbers denote approximate molecular weight in kD) in aqueous solutions has been used. This system undergoes a irreversible cylinder to sphere transition upon addition of N,N-dimethylformamide (DMF) as cosolvent or upon heating. This feature allowed to quantitatively compare chain exchange kinetics in both morphologies. The kinetics were accessed by using hydrogen/deuterium labeling and time-resolved small-angle neutron scattering experiments employing a stopped flow apparatus by which the kinetics could be followed from about some hundreds of milliseconds up to hours. The results show th...