Background: Controversial evidence exists regarding the metastasis-suppressor or promoting activity of motility-related protein-1 (MRP-1/CD9) in breast cancer (BC). Objectives: we aimed at investigating the possible correlation of CD9 with a metastasis marker matrix metalloproteinase 9 (MMP9) in human BC tissues. Methods: A total of 19 BC and 5 normal breast tissues were analyzed. The mRNA expression of CD9 and MMP9 was measured by quantitative PCR. The correlation of genes’ expression with each other and clinicopathological features (i. e. tumor pathology, grade, estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER-2), P53, and KI67) was tested by relevant statistical analysis methods. Results: There was no significant difference between patients with BC and the control group regarding the expression of MMP9 (P = 0.394) and CD9 (P = 0.887). A significant strong positive correlation was observed between CD9 and MMP-9 expressions (r = 0.761 and P = 0.0002). The MMP9 expression was significantly higher in ER or PR positive compared to ER or PR negative tumors (P = 0.046). Conclusions: Given the strong correlation with MMP9, it seems that CD9 might have a role in metastasis in human BC. However, much more studies are required to further support this hypothesis.