Periostin (PN) is a secreted protein that shares a structural homology to the axon guidance protein fasciclin I in insects. Previously, we reported that PN expression is up-regulated in epithelial ovarian tumors. We further examined the role of PN in ovarian cancer. PN is expressed in several normal tissues but not in normal ovaries and has a tendency for higher expression in fetal tissues. Ovarian cancer cells secrete PN, which can accumulate in malignant ascites of ovarian cancer patients. Purified recombinant PN supports adhesion of ovarian epithelial cells that can be inhibited by monoclonal antibodies against α_Vβ₃ or α_Vβ₅ integrin, but not by anti-β₁ integrin antibody. Furthermore, α_Vβ₃ integrin, but not β₁ integrins, colocalizes to the focal adhesion plaques formed on PN. Cells plated on PN form fewer stress fibers and are more motile compared with those plated on fibronectin. We propose PN functions as a ligand for α_Vβ₃ and α_Vβ₅ integrins to support adhesion and migration of ovarian epithelial cells.