Objective— Angiogenesis is an important biological process during development, reproduction, and in immune responses. Placental growth factor (PlGF) is a member of vascular endothelial growth factor that is critical for angiogenesis and vasculogenesis. We generated transgenic mice overexpressing PlGF in specifically T cells using the human CD2-promoter to investigate the effects of PlGF overexpression. Approach and Results— Transgenic mice were difficult to obtain owing to high lethality; for this reason, we investigated why gestational loss occurred in these transgenic mice. Here, we report that placenta detachment and inhibition of angiogenesis occurred in PlGF transgenic mice during the gestational period. Moreover, even when transgenic mice were born, their growth was restricted. Conclusions— Conclusively, PlGF overexpression prevents angiogenesis by inhibiting Braf, extracellular signal–regulated kinase activation, and downregulation of HIF-1α in the mouse placenta. Furthermore, it affected regulatory T cells, which are important for maintenance of pregnancy.