In this article, the focus is on task construction and the importance of this process to develop and promote classroom communication in mathematics. The students’ tests, examination of students’ mathematical work, the teachers’ lesson plans, and reports of the lessons’ instructions are the basic data for this article. The analysis indicated that teachers develop their professional decision-makers through developing the ability to construct relevant tasks for identifying the critical aspects in students’ learning. The findings suggest that construction of tasks can be a productive basis in helping teachers to make fundamental changes in their understanding of what they should focus on in a teaching situation to improve mathematical communication. In this process, the teachers integrate, in a natural way, the research results from mathematics education.