In this paper, the enhancement of thermal properties of polymer-coated silver nanoparticles by the addition of plasmid DNA is described. Nanoparticles of noble metals such as gold and silver possess specific characteristics by virtue of their quantum size effects. Therefore, noble metal nanoparticles are used for chemical sensing and biosensing applications based on their localized surface plasmon resonance absorption that can be measured in the visible region. The polyvinylpyrrolidone (PVP)-coated noble metal nanoparticles, in particular, with high dispersion ability in water, offer several advantages for sensing applications. However, some difficulties are encountered in the use of these PVP-coated noble metal nanoparticles for sensing applications due to their poor thermal properties. To improve the thermal properties of PVP-coated noble metal nanoparticles, we found that the addition of plasmid DNA to PVP-coated silver nanoparticles enhances their thermal properties due to good thermal stability of DNA. The introduction of plasmid DNA into PVP-coated silver nanoparticle dispersion enhanced the thermal properties through the formation of a complex between the nanoparticles and plasmid DNA. Furthermore, other polymers such as proteins and polyethylene glycol did not enhance the thermal properties of PVP-coated silver nanoparticles. Thus, the PVP-coated silver nanoparticle–plasmid DNA complex with enhanced thermal properties has a great potential for use in medical and drug delivery applications.