This study analyzes Federico Zuccari’s architectural activity in a unified manner, emphasizing the anti-Vitruvian character of his language, hitherto largely overlooked. In both his realized architectural works and, above all, the numerous drawings preserved in the Albertina and the Victoria and Albert Museum, Zuccari emerges as an inventive and consciously non-classical designer. His language distances itself from the Vignolesque classicism dominant in late sixteenth-century Rome and aligns instead with the post-Michelangelesque experimentations of Florentine artists such as Giambologna, Paggi, Passignano and Allori. The investigation shows that Zuccari was not a painter who approached architecture as a dilettante, but rather a self-aware designer, the author of an original language that integrates theory, practice, and graphic invention, thereby contributing in a significant way to the architectural debate of the late sixteenth century.