Interest in teachers' moves to classroom discourse has started to increase since how teachers respond to students' thinking influences students' learning. The purpose of this study was to investigate the moves used by one sixth grade mathematics teacher at a public middle school in Turkey to support student reasoning in mathematics instruction and their influence on classroom discourse. Six 80-min lessons were analyzed with particular attention to how the teacher elicits, responds to, facilitates, and extends student reasoning. The results revealed that teacher moves mainly included low-potential moves in all categories. The teacher mainly tried to elicit student answers in the lessons and aimed to facilitate their understanding through questioning. He also tended to confirm students' answers and re-represent their thoughts to the class, occasionally adding further information. However, the results showed that the teacher had a dominant role in classroom interactions. Besides, from time to time, the teacher did not focus on student responses and postpone the student reactions. However, the teacher moves that limit student contribution, such as ignoring students' answers and insisting on their own points of view, reduce the depth of classroom interactions and student understanding. In general, the teacher's ability to support student reasoning and facilitate productive classroom discourse was not sufficient.