The return of the Flemish humanist Justus Lipsius (1547–1606) to the Spanish Netherlands and his reconciliation with Catholicism (1591) have defined his image for posterity. Debates about the sincerity of Lipsius' religious beliefs have continued to the present day. Scholars have presented Lipsius' departure from Leiden as the result of external pressure, as effortless, and conducted in secret. By contrast, this article shows that Lipsius' public engagement in the Republic of Letters was instrumental in enabling his reconciliation with Catholicism. Lipsius employed both published and private letters and the rhetoric of friendship to win support for his return to the Southern Netherlands. After his arrival, Lipsius' correspondence and friendship with the Flemish-Spanish Jesuit Martin Delrio (1551–1608) served as a public platform on which the humanist acted out his reconciliation. The article concludes with a discussion as to why Lipsius only published a fraction of his letters to Delrio.