This thesis explores how Christian mission can maintain its credibility amid the social, cultural, and technological challenges of the 21st century. Religious pluralism, globalization, secularization, and the rise of digital communication have radically transformed the frameworks through which the Christian message is conveyed. The church can no longer assume inherent authority; it must rethink its mission, language, and forms of engagement. The study analyzes the historical and theological development of mission concepts, drawing on the paradigm shift theories of Thomas S. Kuhn and David J. Bosch. According to the Missio Dei perspective, mission is God’s sending to the world, in which the church participates. The thesis examines key stages of mission history, postmodern identity dynamics, shifts in global Christianity, forms of digital mission, and contextual and liberation theology approaches. Through an interdisciplinary lens, the study investigates contemporary opportunities, with particular attention to responses of the Reformed Church. It concludes that the credibility of mission is fundamentally relational and communal, requiring openness and a servant presence.