Embryo implantation and decidualization are crucial steps during early pregnancy. We recently showed that nucleolar stress is involved in embryo implantation. This study was to explore whether nucleolar stress participates in mouse and human decidualization. Our data demonstrated that a low dose of actinomycin D (ActD) could induce nucleolar stress in stroma cells. Nucleolar stress promotes the stromal-epithelial transition during mouse in vitro decidualization through nucleophosmin1 (NPM1). Under nucleolar stress, Wnt family member 4 (Wnt4), a decidualization marker, is significantly increased, but decidua/trophoblast prolactin-related protein (Dtprp/Prl8a2) expression remains unchanged. For translational significance, we also examined the effects of nucleolar stress on human decidualization. Nucleolar stress stimulated by a low dose of ActD enhances human stromal–epithelial transition during human decidualization, but has no effects on the expression of insulin-like growth factor-binding protein 1 (IGFBP1). Our study indicates that nucleolar stress may promote only the mesenchymal–epithelial transition (MET), but not for all the molecular changes during decidualization.