This work describes a new approach to anneal metallic nanoparticles at room temperature using atmospheric pressure plasma. Silver nanoparticle (AgNP) films were deposited on quartz substrates using aerosol injection technique. The AgNP films were annealed at 100 C-400 C using rapid thermal processing, and at room temperature by cold atmospheric pressure plasma for 2-15 minutes. Surface plasmon resonance (SPR) of un-annealed AgNP films was observed at 426 nm, which was blue shifted by 5 to 70 nm after cold plasma annealing. The blue shift in SPR was also observed for thermally annealed AgNP films and the shift was similar to that of cold plasma annealing. SEM images showed the similar distribution of AgNPs on quartz substrates for both cold plasma annealed and thermally annealed AgNP films.