Coulomb blockade behaviors in individual Au nanoparticles of 2 nm core diameter in double-barrier structures have been studied by means of noncontact atomic force spectroscopy(NC-AFS) at room temperature. The Au nanoparticles with a 1-decanethiol ligand were chemisorbed by 1,10-decanedithiol molecules of a mixed 1-octanethiol/1,10-decanedithiolself-assembled monolayer coated on a Au(111) surface; these particles were observed through NC-AFS. NC-AFS measurements of the cantilever frequency shift–sample voltage (1f –VS)curves were sequentially conducted on three Au nanoparticles under the same experimental conditions; the 1f –VS curves were found to deviate from the parabolic (1fN) curve in the cases where no extra charge existed on the Au core. The experimental 1fCB(D1f 〓 1fN) and 1fCB=V curves agree well with the theoretical curves obtained using a golden-rule calculation and the same parabolic parameters. All the results, through NC-AFS, suggest Coulombblockade behaviors in the Au nanoparticles at room temperature.