Teacher's pedagogical thinking, professional action and knowledge base are current issues in research on teaching and instruction. Teacher's ability to work flexibly in continuously changing pedagogical settings is of interest of educational experts and researchers. This research examines teacher's tacit pedagogical knowing, which is defined as a teacher's personal thinking and action process in interactive teaching situation through which a teacher finds solutions to surprising and challenging instructional situations, pedagogical moments. Teachers are able to describe their tacit pedagogical knowing afterwards and express reasons for it. The model of teacher's tacit pedagogical knowing with some simplifying patterns offers a possibility to understand this multifaceted and complex phenomenon. Using the model, it is also possible to illustrate the factors that are at the core of teacher's professionality. It would benefit researchers, teachers, student teachers as well as parents and policy makers to understand the professional practices of teachers.