Density functional calculations have been carried out for Ag n NCO − , Ag n NCO, Ag n NCO + and Ag n NCO 2+ clusters with n⩽6. It was found that for small n, charge state has a strong influence on NCO location site. The ground states of the neutral and anionic complex clusters have a dominantly planar structure while most of the cationic complex clusters prefer to three-dimensional structure. In comparison with free NCO, the N–C distances decrease and the C–O distances increase in Ag n NCO − and Ag n NCO, while quite the reverse can be found in Ag n NCO − and Ag n NCO 2+ . The NCO binding energy has a clear odd–even oscillation behavior.