Research on the political mobilization of ethnic minorities has shown that dual ethno-national identification facilitates involvement in political action on behalf of the ethnic group. This study extends this research by proposing that a dual identity can impede political mobilization on behalf of another relevant in-group – the religious community – especially if this in-group is not accepted by the wider society. Using a sample of 641 Muslims of Turkish origin living in Germany and the Netherlands, dual ethno-national identity (Turkish-German/Turkish-Dutch) was examined in relation to religious Muslim identification and religious political mobilization. Dual identity was expected to be indirectly related to lower mobilization via decreased religious group identification. Further, this mediating process was predicted to be stronger for Turkish Muslims who perceived relatively high religious group discrimination. In both countries we found support for the mediating hypothesis, however, the moderating role of discrimination was confirmed only for the Netherlands. Turkish-Dutch identification was associated with lower support for religious political mobilization because of lower Muslim identification only for Turkish-Dutch participants who perceived high levels of discrimination. These findings indicate that a strong dual (ethno-national) identity can undermine minority members’ support for political rights and actions on behalf of a third relevant in-group, and therefore qualify the social psychological benefits of the dual identity model.