Teachers' attributions of student behavior are associated with the decisions they make about how to respond to behavior problems and support their students. This exploratory study investigates teachers' attributions of student externalizing behavior, how attributions vary as a function of teacher and school characteristics, and the association of those attributions with teachers' perceived likelihood of referring students to mental health services or implementing punitive discipline. We provided a sample of U.S. secondary school teachers (N = 426) a vignette depicting a student with oppositional defiant disorder and asked them to describe what was happening with the student. Attributions were categorized as internal to the student (e.g., mental health), external (e.g., problems at home), both (internal and external), and neutral (e.g., "normal teen behavior"). Results indicated the majority of teachers attributed vignette behavior to external factors. Results suggest that teachers indicating both internal and external attributions had increased likelihood of providing a mental health referral. Teacher and school characteristics were also associated with attributions. Results provide support for the importance of considering teachers' attributions of student behavior and the association of these attributions to pathways into mental health services.