What roles do constitutions play in authoritarian regimes? It has long been argued that constitutions have no meaningful function in closed authoritarian settings and serve as window dressing or simply underline a dictator’s dominance. However, more recent research suggests that constitutions, similar to elections and parliaments, may not be a mere pretence but can foster the durability of authoritarian regimes, such as by facilitating coordination between different regime centres. This paper aims to contribute to the debate on authoritarian constitutions by moving beyond this functionalist approach. It argues that constitutions in non-democracies can be dynamic documents at the heart of conflicts between diverse interests within the regime, which their analysis from the optic of regime stability might belie. To do so, we analyse the case of the Iranian constitution, showing that the circumstances that surrounded its drafting in 1979, as well as its revision in 1989, contributed to the document becoming a focal point for the functioning of the Iranian regime while at the same time created a space for a constitutional conflict between the Supreme Leader (SL) and the president. We then focus on the tenures of two Iranian presidents, a reformist Muhammad Khatami (1997–2005) and a neoconservative Mahmoud Ahmadinejad (2005–2013) to understand, firstly, how they employed the constitution in rhetoric and practice. Secondly, we consider the challenges these efforts faced from the Guardian Council (GC), the main judicial body with the authority to interpret the Iranian constitution, closely aligned with the SL. We demonstrate that both presidents frequently invoked constitutional provisions to assert independence and pursue their different political goals. Through an elaborate constitutional procedure, the GC then sought, and mostly succeeded, in safeguarding the status quo characterized by the primacy of conservative institutions. This paper argues that, akin to democracies, constitutions in non-democratic settings are not just successful coordination devices but can be both tools and objects of a conflict between different intra-regime interests. We base our findings on analysis of 478 legal documents published by the GC as well as secondary sources on the history of the Iranian Constitution.