ABSTRACT This article contributes to the debate on secularization and the return of religion by using the social science complexity frame of reference. A trend in many Western countries is the decline in individual religiosity, increase in ‘nones’, growth of non-Christian religions, changes in religion itself, and the visibility of religion in the public sphere. Many sociologists of religion have analyzed the situation by discrediting the theory of secularization and adopting the newer theories of the spiritual turn, desecularization, and post-secularity, while others have maintained that secularization theory is still valid. The complexity frame of reference offers a toolkit that can be useful in resolving this theoretical dilemma. This article contributes to the theorizing of multiple religious trends at various analytical levels. It criticizes the current approaches before it introduces the concept of religious complexity. Finally, it explores the implications of religious complexity for analyses of multiple and varied religious trends.