We report the thin films of amorphous carbon (a:C) matrix containing gold (Au) nanoparticles (NPs) inside it with varying concentrations. This effortless process for the synthesis of amorphous carbon-maintained gold nanoparticles excluded the utilization of reducing ingredients and also elevated stability of gold nanoparticles. Optical attributes of nanocomposite films were well-observed using ultraviolet-visible spectrophotometry. The surface plasmon resonance (SPR) zone of the film was inspected to be red-shifted of 76 nm in its surface plasmon resonance wavelength from 567 nm (Au (19%) - a:C) to 643 nm (Au (28%) - a:C) just by altering the concentration of metal nanoparticles in a matrix. The structural alterations of gold nanoparticles encased in amorphous carbon were explored dealing with x-ray diffraction (XRD) and transmission electron microscopy (TEM). Rutherford backscattering spectroscopy (RBS) analysis shows the metal atomic fraction of Au/a-C nanocomposite to be 6%, 16%, 19%, 20%, 23%, and 28% with varying thickness between 15–25 nm.