While early childhood mathematics education did not play an important role for many years, today the necessity to be attentive to children’s early mathematics learning is no longer in doubt. There is a broad consensus that mathematical learning in kindergarten is more informal than learning in school. To guarantee coherent mathematical learning in kindergarten, pre- and in-service education of kindergarten teachers in mathematics education is becoming more important. Therefore, a sound theoretical foundation and examination of professional knowledge to realize early mathematics education are necessary. We present a theoretically and empirically founded domain-specific model of kindergarten teachers’ professional knowledge. It serves as a framework to plan and realize professional development programs – as an example shows. A qualitative study – worked out in the German context – indicates that this structure can help to analyze kindergarten teachers’ professional knowledge. We indicate how our findings and interpretations connect to issues shared across national contexts.