This essay examines the religious practice of Sor Margarita de la Cruz (1567–1633), a niece of Philip II who spent her adult life as a nun at the Descalzas Reales in Madrid. At the center of Margarita’s devotional practice were highly lifelike polychrome sculptures of the Christ child, which she cradled and clothed, imitating and reinforcing the dynastic rituals of motherhood performed by court women. I argue that Margarita’s engagement with the infant Christ helped her negotiate the boundaries between her religious vocation and her purported duty to bear children and extend the Habsburg line. Especially important to my analysis of the sacred and worldly frameworks of Margarita’s piety is the hagiographical Vida  written by her confessor. Published in an exquisitely illustrated tome, Margarita’s Vida  codified, in both content and material production, her status as an exemplar of the Pietas Austriaca , the fervent Catholicism central to the Habsburg’s self-definition.