It is widely accepted that the early childhood education and care (ECEC) workforce is central to the quality of services. Modernist constructs of quality signal the importance of qualifications for quality, but the preoccupation with qualification levels silences questions about the knowledge required of ECEC professionals. Postmodern perspectives have opened up debates on understandings of professionalism and given voice to those who work in ECEC. However, sociological perspectives of knowledge challenge postmodernism as either creating a dichotomy between modernist technocratic models of professionalism and the ethical models implicated in postmodernism or at worst presenting knowledge as non-existent. Adopting a sociological perspective of knowledge moves away from the dichotomy, enabling a critical consideration of what is the knowledge-base for ECEC, how it is formed, legitimised and applied. Drawing on Bernstein contributes to the debates on professionalism through providing a model for the ECEC knowledge-base that identifies multiple forms of knowledge, representing both theoretical and experiential knowledge. Theoretical knowledge has strong boundaries that provides legitimacy. However, whilst the social origins of experiential knowledge offers legitimacy, it requires greater articulation and scrutiny.