Maspin is expressed aberrantly in pancreatic ductal adenocarcinoma (PDAC), and its function is still unknown. To explore the role of maspin in PDAC, we constructed wild-type maspin-expressing Panc-1 clones (Panc-1-maspin) by transfecting maspin cDNA into Panc-1, a PDAC-derived cell line that lacks maspin expression. As a control, mock-transfected clones (Panc-1-mock) were constructed using the same method. The invasive ability of the stable transfectants was evaluated with an in vitro invasion assay. The ability of Panc-1-maspin cells to migrate through a Matrigel-coated filter was significantly reduced compared to that of Panc-1-mock cells (p=0.012). In addition, we identified the c.1022A>G variant of maspin in human PDAC cells; however, this polymorphism was not involved in the clinical characteristics of PDAC nor did it alter the invasive ability of PDAC cells. The results of the present study indicate that maspin suppresses the invasive ability of PDAC cells.