There is an increasing awareness of Eustathius of Antioch’s importance to the early part of the fourth-century Trinitarian controversies, but he remains an under-studied figure. Examining the epitome of the anti-subordinationist Contra Ariomanitas, the Eustathian authorship of which has only recently been established, this paper considers one aspect of Eustathius’s view of martyrdom with reference to its implications for political theology. It has often been observed that a shift in Christian political theology followed Constantine’s pro-Christian policies. Additionally, some recent scholarship has argued that Eustathius, along with other ‘Nicenes’, was disappointed with the outcome of Nicaea because it failed to suppress the ‘Eusebian’ party. This paper seeks to highlight an ambivalence in Eustathius’s political theology, in the hope of helping to elucidate this wider context. It observes that, in Contra Ariomanitas, Eustathius centralises martyrdom in his depiction of conflict between the church and the devil. It argues that the way in which Eustathius constructs martyrdom in relation to this wider conflict between the church and the devil echoes older, anti-imperial narratives which do reflect upon the current emperor but that Eustathius is less explicit than these narratives in associating the empire with the devil. Whilst Eustathius’s centralisation of martyrdom in Contra Ariomanitas partly points back to the Diocletian Persecution, and therefore attacks Constantine’s former rivals, it simultaneously presents martyrdom as part of an ongoing struggle in which the current world order, and therefore the empire, is normatively at odds with the church. This paper argues that this suggests an ambivalence towards the empire at the time that Contra Ariomanitas was written (c.325-7). This ambivalence is congruent with and reflective of the ambiguities created by Constantine’s new role in the church and the perceived failure of Nicaea. This paper concludes that Eustathius’s use of the concept of martyrdom within his wider narrative of spiritual conflict suggests a continuing unease with the empire, coupled with a reluctance to attack Constantine directly, reflecting what he perceived to be the ambiguous and awkward position of himself and his theological allies in relation to the emperor in the immediate aftermath of Nicaea.