Teachers' efforts to manage classroom social dynamics are associated with students' social and academic adjustment, but the determinants of teachers' use of social dynamics management strategies have remained unexplored. Multiple potential determinants of strategy use were examined in a study of 164 teachers and their 2,986 students in 164 1st, 3rd, and 5th grade classrooms. Teachers who employed more of these strategies were: female, rated by observers as emotionally supportive, expressed compassion for withdrawn students, perceived a more positive classroom social climate, and had students who reported more negative peer relations. Results suggest that teachers' personal characteristics influence their strategy use. In addition, results suggest that teachers' strategy use may be a response to the immediate peer ecology. [This paper was published in "Social Psychology of Education" v22 p795-817 2019.]