Abstract Previous study showed that aberrant HLA-G expression in cancer cells plays important roles in disease progression and it was associated with tumor metastasis and with poor survival in an animal model with ovarian cancer; however, the mechanisms remain to be explored. In this study, we found that HLA-G expression could dramatically decreased the NK cytotoxicity against the ovarian carcinoma cell line (HO-8910) engineered to express HLA-G (HO-8910-G), and matrix metalloproteinase-15 (MMP-15) expression was up-regulated in HO-8910-G cells. Consistent with this, a strong correlation between HLA-G and MMP-15 expression were observed in a cohort of ovarian cancer samples. Knockdown the HLA-G induced MMP-15 expression by small interfere RNA (siRNA) significantly decreased the HO-8910-G cell migration potential and tumor metastasis. Collectively, our study indicated that HLA-G involved in tumor invasiveness or metastasis may rely on the NK cytotoxicity inhibition and induction of MMP-15 expression in ovarian cancer.