Human cytomegalovirus (HCMV) pathogenesis is characterized by multiple organ system involvement due to viral spread to host organs after a cell-associated viremia. The cell type responsible for HCMV dissemination is unknown. Monocytes are the most likely candidate since they are the predominant cell type infected in the blood. However, monocytes are not productive for viral replication and are abortively infected. The results presented here provide a potential answer to this conundrum. We report that primary HCMV infection of monocytes induces transendothelial migration and monocyte-to-macrophage differentiation and that these HCMV-differentiated macrophages are productive for viral replication. Together, our data suggest a novel mechanism for HCMV pathogenesis; HCMV induces cellular changes in monocytes to promote viral replication and spread to host organs.