Xenophanes’ natural science has traditionally been considered of poor value, but in recent decades it has undergone a remarkable rehabilitation. Karl Popper highly praises Xenophanes’ philosophy overall including his scientific investigations. This article reconsiders all Xenophanean fragments and testimonies concerning nature to verify and essentially confirm Popper’s judgement on the basis of specific textual references and to provide an updated overall study on Xenophanes’ research on nature. Not only does Xenophanes pursue scientific interests analogous to the ones of the Milesian sages, but he employs a more philosophically mature approach to his investigations than his Ionian predecessors as he unveils a new method of investigation by rejecting religious anthropomorphism. I argue that Popper’s praise to Xenophanes’ science can be accepted, although it should be taken into account that Xenophanes’ mentality remains archaic and empirically-grounded, yet projected towards a new form of rationality which fully recognizes the potential of Historie, observation and conjecture.