||Gold nanoparticles (Au NPs) are of great interest due to their unique localized surface plasmon resonance (LSPR) effects, which depend on size, shape, and interparticle distance of NPs. While complicated synthetic approaches changing size and shape of NPs can vary the intrinsic LSPR behavior, we suggest a simple way for tuning the LSPR by controlling interparticle interactions with silica-coated gold (Au@SiO2) NPs and poly(ethylene glycol) (PEG). We confirmed Au@SiO2 NP aggregates permit a wide range of optical bandwidth through the polymer-mediated interactions. The interaction-controlled aggregates showed exceptional stability while maintaining the LSPR behavior under harsh conditions. We also show changing experimental conditions including temperature, polymer concentration and time can yield different plasmonic transitions. The detailed structure and mechanism of the transition are explained via small-angle scattering experiments and discrete dipole approximation calculations.