Teachers' knowledge impacts their practices in classrooms. While considerable research has sought to understand teachers' broad emergent literacy knowledge, less is known about the specific knowledge teachers hold regarding early writing. The present study engaged 66 diverse early childhood teachers in five Head Start programs across two states to examine teachers' knowledge for early writing, bringing specificity to our understanding of teachers' knowledge of writing skills and development. To overcome issues of current elicitation materials which employ researcher generated questioning and decontextualized testing formats, we utilized an innovative instrument (The Early Writing Knowledge Assessment: EWKA) to elicit teachers' knowledge and beliefs from three authentic, contextualized child writing samples reflecting distinct, developmental writing skills. Teachers reflected on each sample and responses were coded using a two‐step process and an a priori set of codes derived from established early writing theories. Results indicated that generally, teachers' early writing knowledge aligned with research‐based conceptualizations, however, wide variation existed in the language used. Patterns existed in the components and subcomponents emphasized depending on the developmental skills demonstrated in the sample. Study findings highlight the wide variability, including inaccuracies, of teachers' early writing knowledge and the inconsistent language used to describe writing development used in the field, both of which have implications for research and practice. Implications for the field, including the potential use of the EWKA to better understand the workforce and for use in professional learning are further discussed.