The effectiveness of the Organisation of Islamic Cooperation (OIC) was challenged after the suspension of Syria’s membership in 2012. There were already indications of Iranian–Saudi rivalry on the issue of Syria’s membership, but the 2016 summit held in Turkey became the stage for a very public dispute between the two states. This was not the first time that the OIC had been undermined by interstate rivalry. Formed in 1969 to project an image of political unity among Muslim states, it has often been challenged by the identity politics and geopolitical competition of its member states. This paper studies the factors that contribute to interstate tensions within the OIC and its approaches to addressing it. By examining a series of OIC events during the period 2012–18 through the lens of critical discourse analysis, it argues that identity politics in the form of sectarianism have been employed, more overtly since the Arab Spring, by both Iran and Saudi Arabia to promote their geopolitical agendas with direct implications for the coherence of OIC. The rivalry not only threatens to fracture the OIC but also makes the notion of Muslim unity nothing more than a mirage.