In this contribution the question is raised how the relationship between anthropology and the science of Islam (Islamic Studies) has developed since the beginning of the institutionalization of both traditions as academic disciplines at the turn of the 20th century. Starting from the observation that from the foundation of social and cultural anthropology to the 1960s, Islam hardly found consideration as an empirical field, this essay discusses the function Islam had taken in the discursive structure of anthropological research. The essay draws particular attention to the German anthropologist Leo Frobenius (1873–1938), who as one of the few anthropologists engaged in a vivid yet short lived discussion with the just emerging science of Islam over the role of Islam in cultural diffusion. Using his image of Islam as an example, the difference of the anthropological design of Islam and that which the science of Islam has created will be explored. Finally, the essay addresses the consequences for both academic traditions which follow from the crumbling of the epistemological wall erected some 100 years ago due to the differentiation between social sciences and geisteswissenschaften.