This article analyzes Josephus' approach to Abraham and astronomy/astrology in Ant. 1.154-168. This retelling of Genesis 12 describes Abraham as inferring the one-ness of God from the irregularity of the stars, thereby implying his rejection of "the Chaldean science" for Jewish monotheism. Soon after, however, Josephus posits that the patriarch transmitted astronomy/astrology to Egypt, appealing to the positive connotations of this art for apologetic aims. Towards explaining the tension between these two traditions, I first map the range of early Jewish traditions about Abraham and the stars, and then consider the Hellenistic discourse about astral wisdom as the domain of ancient "barbarian" nations, as it shaped Hellenistic Jewish traditions that celebrate Abraham's astronomical/astrological skill. I conclude with Josephus' own cultural context, proposing that the attitudes towards astronomy/astrology among his Roman contemporaries may help to account for the ambivalence in his characterization of Abraham as both Chaldean scientist and father of the Jews.