Dual-function theranostic micelles of amphiphilic triblock polycarbonates that allow the possible targeted drug release and simultaneous ratiometric fluorescence sensing in response to H₂O₂ are reported. The disassembly and fluorescence behaviors of micelles are highly influenced by the structural features of the H₂O₂-reactive core-forming hydrophobic blocks. DLS and TEM results indicate that the aliphatic boronate-bearing micelles swell to loosely-aggregated micro-sized nanostructures whereas the aromatic boronate-bearing micelles undergo a complete disassembly giving small fragments instead upon the treatment of H₂O₂. Correspondingly, two micelles exhibit different fluorescence response kinetics and magnitudes. Furthermore, cell uptake study, in vitro cytotoxicity analysis, and drug surrogate release experiment monitored by fluorescence resonance energy transfer confirm that the micelles are biocompatible and feasible for the targeted drug delivery application. Collectively, the study provides molecular insights into design of targeted dual-function theranostic nanocarriers with effective disassembly as well as ratiometric fluorescence signaling.