Improving teacher selection is an important strategy for strengthening the quality of the teacher workforce. As districts adopt commercial teacher screening tools, evidence is needed to understand these tools' predictive validity. We examine the relationship between Frontline Education's TeacherFit instrument and newly hired teachers' outcomes. We find that a one SD increase on an index of TeacherFit scores is associated with a 0.06 SD increase in evaluation scores. However, we also find evidence that teachers with higher TeacherFit scores are more likely to leave their hiring schools the following year. Our results suggest that TeacherFit is not necessarily a substitute for more rigorous screening processes that are conducted by human resources officials, such as those documented in recent studies. [Additional support was provided by the Multidisciplinary Program in Inequality and Social Policy at the Harvard Kennedy School.]