There is a global tendency towards evidence-based practice in education, meaning that practice is molded by research that prescribes “what works” to achieve predefined outcomes. This may present serious pitfalls. Considering that early childhood education in all affluent regions and beyond has to deal with social and cultural diversity, professionals will have to work in contexts of unpredictability and complexity. In this manuscript we develop the central pedagogical questions regarding respect for diversity and their consequences for the professionalization of the early years workforce. Professionalism needs to be understood as systemic and reflective. This may be in tension with evidence-based practice, as the latter leads to standardization and prescription, reducing the discretionary space of professionals. Moreover, evidence-based practice may represent serious democratic deficits, excluding children and parents from the societal debate about what early childhood education is for.