We detect vacancy clusters at Au nanoparticle surfaces using a combination of positron lifetime spectroscopy, 1-detector, and 2-detector measurements of Doppler broadening of annihilation radiation. Gold nanoparticles are formed by MeV implantation of gold ions into MgO (100) followed by annealing. Clusters of two Mg and two O vacancies (v(4)) are attached to the gold nanoparticle surfaces within the projected range (R-p).