Research into the history of alchemy and Paracelsianism in Italy has highlighted the role of Italian courts in the sixteenth and seventeenth centuries as centres of elaboration and diffusion of alchemical knowledge. Among these, one of the best known is the Medici court which already dedicated spaces in the ducal foundry to the alchemical arts in the time of Cosimo I. This interest would remain alive with Francesco I and his son, Don Antonio de' Medici, one of the greatest supporters of Paracelsian medicine in Italy. This contribution presents previously unpublished sources, now preserved in the Archivio di Stato di Firenze and in the collection of the Biblioteca degli Intronati in Siena, that can help us reconstruct in greater detail some significant aspects of Medici alchemical engagement and can, above all, help further determine Paracelsus’s influence in seventeenth century Florence.