Purpose This study aims to determine the factors that influence the decisions of Muslims in Indonesia, the world’s largest Muslim country and recently acknowledged as the world’s most generous country (CAF, 2017), to donate money through mosques. Design/methodology/approach This study uses the extended theory of planned behaviour to determine the above-mentioned factors. Primary data were obtained via a survey that generated 235 responses from respondents in Depok City, Indonesia. The primary data were analysed using descriptive statistics and structural equation modelling. Findings The findings suggest that stronger religious beliefs, a greater trust in mosques, ease of making donations, the influence of significant others and good past experiences of donating to mosques influence donations to mosques in Depok. Thus, most of the hypotheses tested are accepted. However, the relationships between attitude and intention and moral norms and intention are found to be insignificant, which the authors presume to be related to the collective culture of Muslims in Indonesia. Practical implications The managements of mosques need to build, maintain and increase the trust of their congregations in the institution. They also need to improve the services they provide to their congregations and endorse charitable activities through influential persons such as ulama and celebrities. Together with the other stakeholders, such as the government and Muslim communities, they should also improve access to donate and increase the impacts of the donations. Originality/value This study offers fresh and current insights into voluntary giving behaviour to a specific religious institution/channel in the world’s largest Muslim country, which has also recently been acknowledged as the world’s most generous country.