It has been suggested that Christianity is inextricably linked with secularization due to its emphasis on purification and rationalization. But if we believe secularization in Europe is at least partly caused by internal developments within Christianity, may we then assume that secularization emerges wherever Christian missionaries are successful? Has the Christian mission unwittingly instigated secularization in its mission fields? This literature review analyses the argument that American anthropologist Elmer Miller made in the article “The Christian Missionary, Agent of Secularization” (1970) and explores whether his thesis has been confirmed in academic literature during the past fifty years. Miller presents rationalization as the primary driver of secularization and explains how missionaries have played a decisive role in this process. This paper demonstrates that while rationalization has often been mentioned as an effect of the Christian mission in other sources, the process has rarely been linked to secularization in the mission field.