A critical step in establishment of human pregnancy is the invasion of the uterus wall by the extravillous cytotrophoblast (EVCT), a process regulated by multiple autocrine and paracrine factors. Hormones belonging to the GH/prolactin family are expressed at the maternofetal interface. Because they are involved in cell motility in various models, we examined the possible regulatory role of human placental GH (hPGH) in EVCT invasiveness. By using an in vitro invasion model, we found that EVCT isolated from first-trimester chorionic villi and cultured on Matrigel secreted hPGH and expressed human GH receptor (hGHR). These data were confirmed by in situ immunohistochemistry. EVCT expressed the full-length and truncated forms of hGHR, and the Janus kinase-2/signal transducer and activator of transcription factor-5 signaling pathway was activated in EVCT by hPGH treatment. Strong hPGH and hGHR expression was observed when EVCT invaded Matrigel and moved through the pores of the filter on which they were cultured. hPGH stimulated EVCT invasiveness, and this effect was inhibited by a Janus kinase-2 inhibitor. Interestingly, hPGH was more efficient than pituitary GH in stimulating EVCT invasiveness. These results offer the first evidence for a placental role of hPGH and suggest an autocrine/paracrine role of hPGH in the regulation of trophoblast invasion.