Cytomegalovirus (CMV)-specific hyperimmunoglobulin (CMV-HIG) is used to treat and prevent CMV infection in immunocompromised patients, and anti-CD20 monoclonal antibody is successfully used in the treatment for post-transplant lymphoproliferative disease caused by Epstein-Barr virus (EBV). Two immunological approaches have been suggested to further improve the control of viral reproduction in patients with active disease: first, the use of monoclonal antibodies with specificity against viral epitopes and second, coadministration of cells with the capacity to promote antibody-dependent cell-mediated cytotoxicity. Here, we have evaluated the effectiveness of these strategies in vitro (alone and in combination) with neutralization and cytotoxicity assays. Our results indicate that monoclonal antibodies (in particular SM5-1) can be as effective as CMV-HIG in neutralizing-cell-free CMV. Moreover, our data indicate that antibody-mediated elimination (either by moAb or by HIG) of EBV-infected cells can be significantly enhanced by NK cells. Using human NK cells that have been purified, cultured and expanded under GMP conditions, we were able to demonstrate that the combination of NK cells and antibodies could represent a feasible and highly effective clinical approach to achieve control of EBV infections. Especially in leukopenic patients with low numbers of ADCC-promoting cells, the combination of adoptively transferred NK cells and antiviral antibodies offers a promising strategy that should be tested in clinical trials.