Epidermal growth factor (EGF) family ligands have been implicated in cardiovascular diseases because of their enhanced expression in vascular lesions and their promoting effects on growth and migration of vascular smooth muscles cells (VSMCs). Betacellulin (BTC), a novel EGF family ligand, has been shown to be expressed in atherosclerotic lesions and to be a potent growth factor of VSMCs. However, the molecular mechanisms downstream of BTC involved in mediating vascular remodeling remain largely unknown. Therefore, the aim of this study was to examine the effects of BTC on signal transduction, growth and migration in VSMCs. We found that BTC stimulated phosphorylation of EGF receptor (EGFR) at Tyr1068, which was completely blocked by an EGFR kinase inhibitor, AG1478. BTC also phosphorylated ErbB2 at Tyr877, Tyr1112, and Tyr1248, and induced association of ErbB2 with EGFR, suggesting their heterodimerization in VSMCs. In post receptor signal transduction, BTC stimulated phosphorylation of ERK1/2, Akt, and p38 mitogen-activated protein kinase. Moreover, BTC stimulated proliferation and migration of VSMCs. ERK and Akt inhibitors suppressed the migration markedly and proliferation partially, whereas p38 inhibitor suppressed the migration partially but not the proliferation. In addition, we found the presence of endogenous BTC in condition medium of VSMCs, and an increase of BTC upon angiotensin II stimulation. In summary, BTC promotes growth and migration of VSMCs through activation of EGFR, ErbB2, and down stream serine/threonine kinases. Taken together with the expression and processing of endogenous BTC in VSMCs, our results suggest a critical involvement of BTC in vascular remodeling.