The profound changes in communication technology and dramatic increase in global migration have challenged the conventional dyadic conceptualization of ‘domestic’ and ‘foreign’ publics and increased the importance of diaspora publics. Using the four-quadrant model of public diplomacy and cascading activation model of framing, this article analyses the complex role of diasporas in the public diplomacy equation. To illustrate a public-centred and public-based public diplomacy initiative from a non-Western perspective, the article focuses on a Turkish diaspora organization’s attempts to control communication in the aftermath of the 2016 failed coup attempt in Turkey. The analysis reveals how partner publics became adversarial diaspora and transformed into a non-state actor challenging the Turkish state’s legitimacy in the international arena. This case study sheds light on the dynamic transformations of non-Western publics from domestic partners into adversarial diasporas and it questions the dominant Western conceptions of static state-centred, state-initiated public diplomacy.