Myostatin is a highly conserved secretory protein that negatively regulates muscle development by affecting both proliferation and differentiation of muscle cells. In human placentae the expression of myostatin is negatively correlated with gestational age and in placental explants, myostatin acts to facilitate glucose uptake. Expression of the myostatin protein is known to be significantly increased in the placenta of women with pregnancies complicated by preeclampsia. Proper placental development is crucial for a healthy and successful pregnancy. The actions of myostatin on placental cell function are unknown. Here, we describe localization of myostatin through the use of immunohistochemistry and immunocytochemistry in extravillous trophoblast (EVT) of third trimester human placentae and EVT cells isolated from first trimester human placentae. For the first time the effect of myostatin treatment on placental cells is described. Treatment of an EVT cell line (HTR-8/SVneo) and primary isolated EVT with varied concentrations of myostatin (0.001-10μg/ml) resulted in a significant increase in proliferation (HTR-8/SVneo; p<0.0001) and migration (HTR-8/SVneo and primary isolated EVT; p<0.05), effects were both in a dose dependent (proliferation) and independent (migration) manner. We postulate myostatin to an important regulator of placental development and function.