This article first presents a codicological and paleographical analysis of the Bibliotheca Medicea Laurenziana’s manuscript Plut. 57.12, a codex containing the Epistolographi Graeci that was owned and annotated by Francesco Filelfo. The original nucleus of this composite was produced in Constantinople in the third decade of the 15th century. Afterwards, Filelfo himself had two copyists – one of whom is identifiable as Gerard of Patras – transcribe supplements to be added to the codex. Filelfo’s ownership is proved not only by autograph mar- ginal notes, but also by the use of this manuscript as the source of Filelfo’s Latin translation of several of these pseudepigraphic letters that were incorporated in his Commentationes Florentinae de Exilio, and by the correspondences between the marginalia accompanying the Commentationes and those in the Laur. Plut. 57.12.