This research discusses religious dimensions in the environmental adaptation process of two Muslim communities on the northern coast of Java as they face extreme environmental change. Challenged by drowning condition due to rapid coastal abrasion, regular tidal flooding and inundation, communities respond with strategies of coastal adaptation (protect, accommodate and relocate). By employing religion and adaptation as a conceptual frame, this research aims to explore the contribution of religion in adaptation process from Muslims‘ perspectives. Two Muslim communities are selected as religion play as contributing factors in their adaptive strategies: the first case is the Muslim community in Bedono, Demak, Central Java, and the second is the Muslim community in Pantai Bahagia, Bekasi, West Java. Interviews, group discussions, and direct observation are applied as research methods for gathering data. Findings show that in both communities, there are religious interpretations and practices that contribute to communities‘ adaptation process. The further analysis argues two main points. First, the exploration of religious contribution in adaptation process indicates two types of contribution, direct and indirect. Direct contribution is related to the communities‘ coping process as religious practices (such as istighosah, blessed water, shalawat and dzkir) play important role in relieving stress due to the crisis. While indirect contribution present in communities long-term adaptation process as religious interpretation and practices intertwined with other contributing factor of adaptation, especially economic and social factors. Second, this research also explores intra-religious diversity in Muslim communities as result of communities‘ dynamics in adaptation process. Findings indicate two trend of intra-religious diversity–tension due to intensifying strict Muslim interpretation in Bedono and compromising differences to maintain economic ties in Pantai Bahagia. These varieties of religious interpretations and practices also contribute to adaptation process in both selected Muslim communities. Keywords: Religion and Adaptation, Coastal Adaptive Strategy, Intra-religious Diversity, Muslim Communities, North Coast of Java, Extreme Environmental Changes