Scholars often saw 'Sidereus nuncius' as inaugurating a novel genre of scientific writing; one that mixes elements of astronomy and natural philosophy, mixed-mathematics and travel reports, cosmography and the conventions of baroque drawing, elements of humanist pedagogy and elements of natural history. Although some of these influences were subject of extensive treatment, the natural historical elements of 'Sidereus nuncius' were, comparatively, less carefully investigated. And yet, as I will show in this paper, the natural historical outlook of 'Sidereus nuncius' played (...) a significant role in its reception. My purpose in this paper is to investigate some of the elements of natural history present in 'Sidereus nuncius'. Firstly, I show that in writing Sidereus nuncius, Galileo often made appeal to the “specialized observations” and “expert reports” of natural historians. Secondly, I show that some of the early readers of Sidereus nuncius, such as Johannes Kepler and Francis Bacon, read Galileo’s book as a natural history. I also discuss the ways in which some of them were read and interpreted in the same vein by some of Galileo’s early readers, such as Johannes Kepler and Francis Bacon. (shrink)