Catechins, a family of polyphenols found in tea, evoke various responses, including cell death. However, the side effects of these compounds, particularly those on embryonic development, have not been characterized in detail. A previous study by our group showed that (-)-epigallocatechin-3-gallate (EGCG), a catechin highly abundant in green tea, induces different cell-death modes in MCF-7 cells, depending on the treatment dosage. In the current study, we examined the effects of EGCG on mouse embryos at the blastocyst stage, subsequent embryonic attachment and outgrowth in vitro and in vivo implantation by embryo transfer. Blastocysts treated with 25-50 μM of EGCG exhibited a significant increase in apoptosis and a corresponding decrease in total cell number. Notably, the implantation success rate of blastocysts pretreated with EGCG was lower than that of their control counterparts. Moreover, in vitro treatment with 25-50 μM of EGCG led to increased resorption of postimplantation embryos and decreased fetal weight. EGCG appeared to induce injury in mouse blastocysts through intrinsic apoptotic signaling processes to impair sequent embryonic development. These results collectively highlight the potential of EGCG to induce embryonic cytotoxicity.