Religious organisations (ROs) are often said to play an important role in mitigating the impact of HIV/AIDS. Yet, limitations of that role have also been acknowledged. While most of the literature has focused on ideological and individual-level implications of religion for HIV/AIDS, in this study, we shift the focus to the organisational factors that shape and constrain ROs' involvement in both HIV prevention and HIV/AIDS care and support. Using primarily qualitative data collected in a predominantly Christian area in southern Mozambique, we show that the organisational vitality of a RO as determined by its membership size and its relationships with other churches and with governmental and non-governmental agencies is a pervasive priority of RO leaders. Therefore, all church activities, including those related to HIV/AIDS, are instrumentalised by the religious leadership to achieve the church's organisational aims—maintaining and growing its membership, safeguarding the often precarious coexistence with other churches, and enhancing its standing vis-à-vis the government and powerful non-governmental organisations. As a result, the effectiveness of ROs' involvement in HIV/AIDS prevention and assistance is often compromised.