The focus of this study is to examine the challenges of multiculturalism and religious modernism faced by the Catholic Church in Indonesia based on an ecclesiological perspective. The Catholic Church in the context of Indonesian society, which is rich in cultural and religious diversity, faces complex dynamics that affect its religious practice and identity. The methodology of writing this paper is through literature studies and accurate information sources. This study uses the concept of ecclesiology to examine the impact of multiculturalism and religious modernism, with the aim of understanding the role and mission of the Catholic Church in Indonesia in the context of the challenges of multiculturalism and religious modernism. This study is expected to provide a basis for the development of more effective pastoral strategies, strengthen the identity of the Church, and increase the contribution and contribution of the Catholic Church in supporting Indonesia's diversity. The Catholic Church is expected to be more adaptive to changes in the social and religious environment, inclusive, transformative, agent of consolidation, herald of love and peace, glue unity and unity of the nation, by making the concept of ecclesiology as a foundation to answer existing challenges.