Immediately following Acts 15’s climactic apostolic accord deeming unnecessary the circumcision of Gentile converts but imperative that they follow fundamental behavioral guidelines, the circumcision of Timothy by Paul seems to inspire in scholars fascination and ambivalence in equal measure. A difficult passage to incorporate within the wider narrative of Acts and even Paul’s own testimony, 16:1-5 brings to the forefront the complexities of ethnic discourse. In this paper, I argue that this passage engages directly in ethnic discourse that plays upon Timothy’s disputed ethnicity. His mixed heritage is an immediate test of the preceding chapter’s consensus that Gentile converts were not required to follow the full strictures of Judaism, yet the text exhibits no dissonance between this theological compromise and Paul’s circumcision of Timothy. In contrast, scholarly efforts to disentangle the ethnic reasoning behind this passage demonstrate unease with the pliability and constructed nature of ethnic identities. After discussing the passage’s history of interpretation, the complexity surrounding the proper translation in Acts of the ethnic appellation Ioudaios, and the ambivalent function of circumcision as a marker of ethnicity, I argue that Luke’s Paul engages precisely in that definitive ethnic discourse that posits the rigidity of ethnic distinctions yet admits their pliability. Asking whether Timothy was a Gentile or a Jew creates a simple binary where ethnic complexity actually exists. From Luke’s perspective, Timothy’s ethnicity is concrete and embodied but also pliable and negotiable. In significant ways, Timothy is both Jew and Hellene; he dwells in a complex ethnic space created by his Jewish mother and Hellene father. This analysis also begins to demonstrate that Acts aims not to eradicate ethnic and racial differences under a homogenizing Christian identity but to demonstrate how the flexibility of ethnic identities played a critical function in the spread of the Jesus movement.