Nuclear domains 10 (ND10s) are discrete subnuclear structures that contain the three major protein components promyelocytic leukaemia protein (PML), hDaxx and Sp100. Previous studies identified the ND10-components PML and hDaxx as cellular restriction factors that independently counteract human cytomegalovirus (HCMV) infection via the repression of viral immediate-early (IE) gene expression. Consequently, we asked whether Sp100 is likewise involved in this repressive activity. Infection of Sp100 knockdown (kd) cells with HCMV resulted in a significantly increased plaque-forming ability. In addition, ablation of Sp100 led to a considerable increase in the number of IE1-expressing cells, indicating that Sp100 suppresses the initiation of viral gene expression. Next, double-kd cells, lacking either Sp100/hDaxx or Sp100/PML, were generated. Here, infection resulted in an additional enhancement in HCMV replication efficacy compared with the single-kd cells. Thus, our results further strengthen the concept that the three major ND10-components independently contribute to the cellular restriction of HCMV replication.