One of the major conflictscontinuously occurring in Malaysia is the issue of race and religious relationships. Today, houses of worship in Malaysia have always been seen as isolated entities that can add to race relations and nation-building conflicts. This issue has led to the planning of houses of worship as nation-building elements in forging social inclusion among the different religious buildings of other faiths. Therefore, this research aims to evaluate mosques' social inclusion characteristics, which can contribute to the more extensiveframing of Malaysian planning policy on the sustainable designof houses of worship. Toreflect the ideal of SDG 11, Sustainable cities and communities and SDG 16, Peace, justice and strong institutions, it is essential to identify social inclusivity as one of theprimarydesign approachesforany Islamicinstitutionsand mosques designs. Should the mosques be part of the nation-building entities and notjust community centres for each faith? This research covers selected case studies mainly inKuala Lumpur, representing the city with the most educated and diverse multi-faith context. Four significant mosques were selected and studied through observationsand interviews data collection approach. The research findings indicate that elements such as scale, massing, permeability, visibility, territoriality, and iconic imagery are essential to design criteria for mosques. Significantly, this research provides suggestionsand guidelines for designers and committee leaders of all religions in Malaysia to re-look at the activities and planning aspects of their houses of worship. Furthermore, it helps to promoteinclusive elements such as social interaction, tolerance, and understanding of different religious beliefs. Hence, accepting these multi-faith centres will create a moreintegrated, harmonious and sustainable community.