[en] We examine the origin of the surface-enhanced Raman scattering (SERS) background mediating with a graphene monolayer at Au nanoparticle-Au thin film junctions. We find the degree of the asymmetric shape of the radial breathing like mode (RBLM) peak at 150 cm"−"1 is strongly correlated with the accompanied SERS background intensities. The SERS investigation with the out-of-plane modes (300∼700 cm"−"1) of graphene gives significant clues that the SERS background, the degree of the tilted formation from the analysis of the transverse acoustic peaks, and the spectral shape of the RBLM peak are strongly correlated with each other, indicating that electron–phonon coupling plays a crucial role in increasing the SERS background. (paper)