This paper describes a novel route to the synthesis of core–shell nanostructures utilizing Nitroxide Mediated Radical Polymerization (NMRP). The hybrid nanostructures with nanogold cores and precisely designed polystyrene shells (PDI < 1.3) have been synthesized through late injection of TEMPO coated gold nanoparticles into a TEMPOL (4-hydroxy-TEMPO) mediated styrene polymerization system. Thermal analyses have shown that the thus obtained polystyrene modified gold nanoparticles are significantly more stable to the thermal treatment than only thiol-stabilized gold nanoparticles (aggregation has not been observed even at 300 °C). The obtained materials exhibit intensive surface plasmon resonance (SPR) observed near 520 nm that provides an opportunity to apply them as high-temperature optical sensors. The proposed procedure allows for precise synthesis of tailor-made nanohybrids via macroradical coupling.