Supramolecular aggregates of stimuli-responsive block copolymers are increasingly utilized as drug nanocarriers. Although in situ tracking their triggered disintegration and drug release processes at the cellular level is highly desirable, it remains a considerable challenge. We report the fabrication of double hydrophilic block copolymers covalently conjugated with alpha,beta-unsaturated ketone-caged coumarin functionalities in the thermoresponsive block. Upon thermo-induced micellization and cellular uptake, Michael addition reaction of unsaturated ketone moieties with thiol compounds (GSH and Cys) in the reductive subcellular compartments leads to micelle-to-unimer transition. This is accompanied by concomitant fluorescence emission turn-on and triggered drug release, allowing for the process visualization.