A polymer colloidal solution having dispersed nanoparticles of Ag metal has been developed using a novel chemical method. Colloidal solutions of representative concentrations of 0.2 to 5.0 wt% Ag-nanoparticles contents in the primary solutions were prepared to study the modified ultrasonic attenuation and ultrasonic velocity in polyvinyl pyrrolidone (PVP) polymer molecules on incorporating the Ag-nanoparticles. The synthesized silver nanoparticles dispersed in the polymer solutions were characterized byUVVisible absorption spectroscopy, X-ray diffraction (XRD) and Transmission electron microscopy (TEM). The nanofluid sample showed a symmetrical peak at 410 nm due to the surface plasmon resonance of the silver nanoparticles. XRD results confirmed that silver nanoparticles were crystalline in the colloidal solution. The TEMmicrograph revealed spherical silver nanoparticles having diameter in the range 10-30 nm. A characteristic behaviour of the ultrasonic velocity and the attenuation are observed at the particular temperature / particle concentration. It reveals that the colloidal suspension occurs in divided groups in the small micelles. The results are discussed in correlation with the thermophysical properties predicting the enhanced thermal conductivity of the samples.