Silver nanoparticles-polymer nanocomposites, Ag-(1 - x)PVP-(x)PEG, were synthesized by wet chemical method in the presence of polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG). A mixture of two stabilizing agent PVP and PEG is found to play a crucial role in controlling the morphology of nanocrystalline silver particles in the composite. This is inferred based on the shape and size study of nanocrystalline silver using the X-ray diffraction, transmission electron microscopy, Uv-vis spectroscopy, FTIR, and surface enhance Raman studies. These results suggest asymmetrical growth of silver nanocrystalline particles in the presence of both PVP and PEG. Comparison of the thermal properties of the Ag-polymer nanocomposites with pure polymers, PVP and PEG, showed that the thermal stability of the nanocomposite deteriorates by as much as 75 degrees C in the presence of low PEG concentration (x < or = 0.6) and improves by around 45 degrees C at higher PEG concentration (x > 0.6). The study highlight the fact that the morphology of nanocrystalline silver can be altered just by varying the polymer weight ratios rather than any processing parameters, thus offering a novel, simple, and controlled synthesis engineering route to the formation of nanocrystalline silver in polymer matrix.