This paper reported the design and fabrication of microencapsualed n-eicosane with a poly(methyl methacrylate-co-methacrylic acid) shell as a novel type of pH-responsive microencapsulated PCM for multipurpose applications such as thermal energy storage and controlled chemical release by an emulsion-templated in-situ polymerization technology. The spherical morphology and core-shell microstructure of the resultant pH-responsive microcapsules were confirmed and their chemical structure and elemental compositions were identified. Furthermore, their phase change behaviors and thermal energy-storage performance were investigated extensively. The pH-responsive microcapsules not only obtained excellent thermal regulation and thermal management capabilities due to a high phase change enthalpy over 177 J/g and good phase change reversibility, but also presented a well-defined pH-responsive controlled-release behavior by association and dissociation of hydrogen bonding interaction induced by different pH conditions and electrostatic repulsion. The dye release experimental results indicated that a maximum release amount of Rhodamine B could be achieved for the dye loaded microcapsules at mildly acidic pH 5.05. In the light of highly efficient pH-stimuli responsiveness and excellent thermal regulation capability, the pH-responsive microcapsules developed by this study exhibit a great potential for pH-stimuli responsive controlled release applications of temperature/heat-sensitive drugs or chemicals when performing the thermal energy storage and thermal regulation.