The photoabsorption spectra of naphthalene cluster ions, (C10H8)(n)(+) with n = 2-7, in the visible and near-IR (500-1100 nm) spectral regions have been observed by mass-selected photodissociation spectroscopy. These cluster spectre show two distinct absorption maxima centered at 1 mu m and 570 nm and match well the absorption spectra of the dimer ion previously obtained in solutions. The near-IR band is assigned to the characteristic intervaIence transition of the dimer ion produced in these clusters, while the visible band is attributed to a local excitation corresponding to the monomer D-2 <-- D-0 transition. Both absorption bands are found to be independent of cluster size, which is explained by assuming a core structure involving a strongly bound dimer ion. The stability and dissociation dynamics of the ionic clusters are compared with those of the corresponding neutral clusters.