Estrogen signals have been suggested to modulate the progression and metastasis of nonsmall cell lung cancer (NSCLC), which is one of the leading causes of cancer deaths worldwide. While there are limited data concerning the roles and effects of G-protein-coupled estrogen receptor (GPER) on the progression of NSCLC, our present study reveals that the expression of GPER in NSCLC cells is obviously greater than that in lung fibroblast cell line MRC-5. Activation of GPER via its specific agonist G-1 decreases the in vitro motility of A549 and H358 cells and the expression of matrix metalloproteinase 2 (MMP-2) and MMP-9. Further, G-1 treatment can rapidly decrease the phosphorylation, nuclear translocation, and promoter activities of NF-kappa B in NSCLC cells. BAY 11-7082, the inhibitor of NF-kappa B, also inhibits the expression of MMP-2/9, while over expression of p65 significantly attenuates G-1-induced downregulation of MMP-2/9. It suggests that inhibition of NF-kappa B mediates G-1-induced MMP-2/9 downregulation. G-1 treatment significantly down regulates the phosphorylation of I kappa B kinase beta (IKK-beta and I kappa B alpha, while not IKK-alpha, in both 549 and H358 cells. ACHP, the specific inhibitor of IKK-beta, can reinforce G-1-induced MMP-2/9 downregulation and invasion suppression of A549 cells. Collectively, our results suggest that activation of GPER can inhibit the migration of human NSCLC cells via suppression of IKK-beta/NF-kappa B signals. These findings will help to better understand the roles and mechanisms of GPER as a potential therapy target for NSCLC patients.