Previously we reported that G protein-coupled receptor APJ endogenous ligand apelin-13 induced adhesion of monocytes to human umbilical vein endothelial cells(HUVECs).Now we investigated whether phosphatidylinositol 3-kinase (PI3K) signaling pathway mediated monocytes (MCs) adhesion to HUVECs induced by apelin-13. Human umbilical vein endothelial cell line ECV304 was cultured in DMEM medium and the monocyte cell line THP-1 was cultured in 1640 medium. Myeloperoxidase(MPO) assay was used to identify effects of monocytes adhesion to HUVECs. Expression of vascular cell adhesion molecule (VCAM) -1, phospho-PI3K and PI3K were detected by Western blotting. Apelin-13 promoted PI3K phosphorylation in concentration-dependent and time-dependent manner, which reached the peak at 1 μmol/L and 30 min respectively. The PI3K inhibitor LY294002 inhibited PI3K phosphorylation and the expression of VCAM-1 in HUVECs induced by apelin-13. And the PI3K inhibitor LY294002 inhibited the MCs adhesion to HUVECs induced by apelin-13. It can be concluded that apelin-13 promoted monocytes adhesion to HUVECs through VCAM-1 mediated by PI3K signaling pathway.