Abstract: Messianic Judaism, a network of congregations that incorporate Jewish ritual into evangelical worship, is one branch of a fast-growing trend among Christians globally towards ‘Jewish affinity’. Drawing on a multi-site comparison in North America, this article examines one of Messianic Judaism’s most significant internal debates: should non-ethnically Jewish ‘gentile believers’ (GBs) obey biblical laws? It argues that GBs do not simply imitate Jews badly, as outsiders and their own leaders often believe. Rather, their actions are best characterized as mimesis in two complementary forms: mimesis of Jews and ‘mimetic discipleship’ of Jesus-the-Jew. Taken together, these forms offer a heuristic tool sufficiently capacious to explain both individuals’ propensity for Jewish practice and the socially specific ways it is constructed. I conclude that Jewish affinity reflects a key problem in contemporary Christianity, namely what happens when people in one religion (Christianity) come to believe that their God incarnated in the body of a man they now associate with another religion (Judaism)?