Plasmonic heating of gold nanoparticles (AuNPs) under laser illumination is ahighly desirable technique, es-pecially for cancer therapy. However, significant drawbacks still remain including uncontrolled heat release from AuNPs, random exposure duration, and selection of the proper laser power without damaging normal healthy cells. Herein, we demonstrate asimple and versatile method to measure temperature variation on the surface ofAu nanoparticles under laser irradiation based on a thermoresponsive polymer, poly(ethylene glycol) methylether methacrylate (PEGMA). In this context, aseries of PEGMA polymers were synthesized to have different lower critical solution temperature (LCST) values (28–90 8C) and conjugated to the surface of spherical AuNPs by agold–thiolate linkage. According to our strategy, the AuNPs first photothermally absorb light energy and con-vert it to heat owing to their tailored photothermal charac-teristics. The generated heat from the AuNPs subsequently dissipates into the surrounding thermoresponsive PEGMA polymer. When the temperature generated on the Au surface upon laser irradiation for acertain exposure time reach-es the LCST value of the surrounding PEGMA polymer, the polymer chain collapses. Therefore, the hydrodynamic diam-eter of the PEGMA-coated AuNPs changes, which can be easily monitored by using dynamic light scattering (DLS). We systematically measured the temperature (28–90 8C) generated on the AuNP surfaces by using different laser power den-sities with varying durations. We believe that the resulting strategy will be very valuable for oncologists to easily pre-dict the minimum laser power and duration needed tode-stroy the cancer cells through the photothermal effect of Au nanostructures.