Cytotrophoblasts are the key trophoblast cells which differentiate into different trophoblast lineages. In this report, glycodelin-A action on fusion of a cytotrophoblast-like cell line (BeWo) was investigated. It significantly reduced the spontaneous fusion of BeWo cells. The treatment enhanced the invasion and extracellular-signal regulated kinases activation of BeWo cells. The mRNA expression of syncytialization markers, human chorionic gonadotrophin and glial cells missing homolog 1 were suppressed upon glycodelin-A treatment. The data suggest a possible function of glycodelin-A in mediating cytotrophoblast differentiation.