Ovarian cancer causes more deaths than any other type of female reproductive cancer. The development of new therapeutic approaches is required due to the low survival rate using routine methods. The goal of this study was to investigate the effect of the gene silencing of mediator complex subunit 19 (MED19) on cell viability and tumor growth in ovarian cancer. Immunohistochemistry was used to characterize the expression of MED19 in human ovarian cancer tissues. Lentivirus-mediated RNAi was employed to downregulate endogenous MED19 expression in SKOV-3 and HEY ovarian cancer cells. MTT assay, BrdU incorporation assay, colony formation assay, cell cycle analysis and tumor xenografts in nude mice were performed to determine the effects of MED19 silencing on cell viability and tumor growth in vitro and in vivo. The data showed that the expression of MED19 in human ovarian cancer tissues correlated with the level of tumor malignancy. The downregulation of MED19 in ovarian cancer cells significantly inhibited cell proliferation and colony formation in vitro and led to cell cycle arrest in the G0/G1 phase. MED19 RNAi significantly inhibited ovarian cancer tumor growth in engrafted nude mice. Our findings reveal that the knockdown of MED19 by lentivirus-mediated RNAi may be useful in the treatment of human ovarian cancer.