In March 1506, Machiavelli was in the Casentino when he received a letter from Agostino Vespucci in Florence. A few weeks earlier, Machiavelli had arranged for his Decennale primo – a verse history of Florence between 1494 and 1504 – to be printed by Bartolomeo de’ Libri, with Vespucci bearing the costs. It was the first of his works in print and had already met with some success. Much to Vespucci’s alarm, however, a rival printer, Andrea Ghirlandi da Pistoia, was now selling a pirated version, festooned with mistakes. This article explores how Vespucci tried to protect Machiavelli’s interests and his own investment. It shows how Vespucci successfully circumvented the lack of copyright protection by casting the pirated version as a form of defamation and exploiting both secular and ecclesiastical authorities. In doing so, it casts fresh light on the legal and commercial challenges of printing in sixteenth-century Florence.