The relationship between development and religion is an uneasy one. Since the invention of modernisation theory in the 1950s religion has been marginalised-seen as something that would fade as secularisation increased. Although this has not occurred, religion is still considered a taboo subject which falls outside the gamut of development, despite the religiosity of many faith-based development organisations, donors, and recipient communities. In this paper I emphasise the importance of religion to development by tracing religious influences within transnational development networks operating in Aceh, Indonesia, after the 2004 Boxing Day tsunami. Religious influences are analysed amongst donor communities in Australia and New Zealand/Aotearoa; within the activities of religious NGOs in Aceh; amongst recipient communities; and in the physical landscape of Aceh, where the rebuilding of sacred spaces has been slow and difficult. It is argued that the current approach to religion within development, and much development research, is outdated and inappropriate, reflecting and enforcing particular Western divisions between church and state. For more effective aid which attends to local concerns and priorities, transnational development networks need to acknowledge, incorporate, and involve religious spaces and institutions rather than continue to promote a culture of secularism.