Though the crisis over Iran’s controversial nuclear programme has entered its second decade, there is still a lack of clarity on the Iranian leadership’s intentions in this area. Indeed, while Tehran continues to claim that its nuclear programme is merely for peaceful purposes, the international community is not entirely convinced. To effectively convince the world of its peaceful intentions, while keeping the domestic constituencies committed with the programme, despite sanctions, the regime has developed a nuclear narrative. This narrative is certainly a complex affair, comprising two major themes: religion and nationalism. A key plank of the leadership’s argument that the programme is purely civil in nature is that nuclear weapons are prohibited under Islamic law. Tehran further claims that the nuclear programme, which is supported by all factions of the Iranian population regardless of political affiliation and religious background, is pursued to advance scientific and technological progress. In claiming the purely civil character of the nuclear programme, the Iranian leadership has long made the argument that Tehran’s foremost political authority, Supreme Leader Ayatollah Khamenei, has issued a “fatwa”, prohibiting nuclear weapons, which has widely resonated in the west. In parallel to the religious discourse, various Iranian leaders, including former president Mahmoud Ahmadinejad and his successor, President Hassan Rouhani, as well as Khamenei himself, have highlighted the nationalist drivers behind the country’s nuclear programme. Each of these two themes has several strands, which have been highlighted by various actors, depending on the context, the present conditions domestically, regionally, and internationally, and the target audience. These strands encompassed in the religious and nationalist themes include: technological progress, what I refer to as the “enemy narrative”, and Islamic law as a limiting factor. This paper will examine the Iranian nuclear narrative by identifying the function of each strand and its impact on Tehran’s nuclear and foreign policy decision-making. It is informed by extensive qualitative and analytical research, including textual and discourse analysis. The paper examines the much-debated Iranian nuclear programme from a different angle, while contextualising it in the broader defence and development debate in post-revolutionary Iran.