Past research indicates that teacher math anxiety is related to student outcomes and can be decreased through intervention. However, there is little research on this topic, partially due to a lack of math anxiety measures validated for use with practicing teachers. In this study of 399 elementary school teachers, we report on the construct validation of the Math Anxiety Scale for Teachers. Factor analyses support a distinction between components of general math anxiety and anxiety about teaching math. Math anxiety scores correlate with other teacher characteristics in expected ways: higher math anxiety is associated with lower mathematical knowledge for teaching, more traditional beliefs about math teaching and learning, being a lower elementary school teacher, and a lack of math-specific teaching credentials. The 15-item Math Anxiety Scale for Teachers can be administered efficiently in large-scale studies and may support advances in research exploring relations among practicing teachers' math anxiety, instruction, and student learning. [This article was published in "AERA Open" (EJ1210489).]