Inheriting a legacy of imperial competition, the Turkey-Iran rivalry today manifests itself through the contest for leadership of the Arab Middle East, and Muslim hearts and minds more generally. The authors contend that Turkey and Iran’s relationship transcends the boundaries of amity or enmity that traditionally define actors in the modern Middle East state system. Rather, Ankara and Tehran have been able to successfully compartmentalize elements of their rivalry while strengthening bilateral ties and expanding areas of economic cooperation. The authors posit that the present-day Turko-Iranian relationship falls in the category of neither friend nor enemy, but rather that of frenemy.