Colloidal colorimetric microsensors enable the in-situ detection of mechanical strains within materials. Enhancing the sensitivity of these sensors to small scale deformation while enabling reversibility of the sensing capability would expand their utility in applications including biosensing and chemical sensing. In this study, we introduce the synthesis of colloidal colorimetric nano-sensors using a simple and readily scalable fabrication method. Colloidal nano-sensors are prepared by emulsion-templated assembly of polymer-grafted gold nanoparticles. To direct the adsorption of gold nanoparticles to the oil-water interface of emulsion droplets, gold nanoparticles (~11nm) are functionalized with thiol-terminated polystyrene (PS, M n = 11k). These PS-grafted gold nanoparticles are suspended in toluene and subsequently emulsified to form droplets with a diameter of ~30µm. By evaporating the solvent of the oil-in-water emulsion, we form nanocapsules (AuNC) (diameter < 1µm) decorated by PSgrafted gold nanoparticles. The chemical and structural integrity of the AuNC are tested by exposing them to organic solvents. For all solvents, a plasmonic shift is observed due to an increase in the inter-nanoparticle distance caused by the swelling of the PS brush. To test mechanical sensing, the AuNC are embedded in an elastomer matrix. The addition of a plasticizer reduces the glass transition temperature of the PS brushes, and in turn imparts reversible deformability to the AuNC. The plasmonic peak of the AuNC shifts towards lower wavelengths upon application of uniaxial tensile tension, indicating increased inter-nanoparticle distance. The AuNC recovers its original plasmonic peak upon the release of the tensile strain. This study provides a robust and easily scalable method of producing NC-based sensors that can potentially detect the presence of chemicals or small tensile strains at the nanoscale in microelectromechanical systems and biological cells.