This paper examines Ambrose of Milan's exegesis of Rm. 2:17-29 and 3:1-2 and argues that it contributed significantly to shaping an "anti-Jewish" image of Paul in Late Antique Western Christianity. Recent scholarship, particularly within the Paul within Judaism perspective, has stressed the importance of investigating the later reception of Paul's letters alongside their Second Temple Jewish context. Ambrose of Milan offers a particularly revealing case study in this respect. His exegetical activity is rooted in the tradition of allegorical biblical hermeneutics, drawing above all on Philo and Origen of Alexandria, and is clearly reflected in his interpretation of the Letter to the Romans. While Paul affirms the continuing validity of circumcision and the Law (Rm. 3:1-2), even as he criticises their merely outward observance (Rm. 2:28-29) and repeated transgression (Rm. 2:21-23), Ambrose reinterprets these passages to argue that the "second people" (i.e., the Christians) has supplanted the "first" in fulfilling the spiritual precepts of the Law (e.g., Epistulae, 64,1-5). Circumcision thus acquires an exclusively spiritual meaning (cf. Rm. 2:29), rather than an external one (e.g., De Abraham, 78; De officiis, 1,50,251; De fide, 5,13). Only the Church can therefore be identified as the "verus Israel", and its members as the true Jews (e.g., De Spiritu Sancto, 3,22,162). The consequences of this reading are far-reaching: circumcision and Law are deemed to have lost their validity with Christ's coming (e.g., Epistulae, 69,19-24), and Israel - held responsible for Christ's death (e.g. Expositio de Psalmo CXVIII, 12,19) - is excluded from the promises made to the patriarchs (e.g., Expositio de Psalmo CXVIII, 2,9). Ambrose's interpretation was probably further shaped by contemporary historical events, notably the affaire of the synagogue of Callinicum (388), contributing to a distorted understanding of Paul's relationship with first-century Judaism.