Although growing scientific evidence has highlighted beneficial effects of religion and spirituality on mental health and psychosocial well-being, the integration of religious and spiritual needs with mental health and psychosocial support in humanitarian contexts has been identified as a gap. Accordingly, this can be linked to a lack of official related guidelines of how to address these concepts in the humanitarian sector. This issue becomes particularly relevant in contexts where religion and spirituality play a crucial role. This study explores this problem in the context of Indonesia which due to commonly occurring natural disaster is targeted by humanitarian responses, while also being a religious and spiritual country. The purpose of this study therefore responds to this background by discovering the integration of religion and spirituality in mental health and psychosocial support provided by humanitarian organisations in Indonesia and formulating recommendations on the same. This was operationalised through a qualitative approach, and more specifically an embedded single-case study design. Further, the material consists of information retrieved through interviews and documents, from humanitarian organisations selected through snowball sampling. Analysed with the support of the ADAPT model, an adapted version, the IASC MHPSS Guideline, and the additional Faith-Sensitive Guideline, this study concludes that humanitarian organisations operating in Indonesia, either mainstreamed or not, work with mental health and psychosocial support, and thereby also include approaches which consider religion and spirituality. However, while well aware of the contextual needs, in particular the latter is not formally integrated. Accordingly, this study suggests organisational capacity building on the integration of religion and spirituality in MHPSS, based on existing guidelines and institutional knowledge and capacity, in order to ensure and improve proper humanitarian responses.