The re-discovery of Diego Hurtado de Mendoza’s herbaria in the Library of El Escorial allows us to offer a somewhat different look at the library of this aristocrat, diplomat, collector and poet from Granada. As his library passed into the hands of Felipe II when Mendoza died in 1575, the herbaria were incorporated into the whole cultural, political and artistic program of the Royal monas- tery-palace-mausoleum. This paper aims to propose a new look to these herbaria within the two cultural contexts in which they lived. Both based, not only in the Mendoza’s library as a space of constructing knowledge about the natural world, but also playing different roles inside a library which had moved between Italy (Venice, Trent, Padua, Bologna, Rome) and Spain (Granada, Madrid, El Escorial) over four decisive decades for the future of the Catholic Monarchy.