The Vanderbilt Assessment of Leadership in Education (VAL-ED) is a multirater assessment of principals' learning-centered leadership. The instrument was developed based on the Standards for Educational and Psychological Testing. In this article, we report on the validity and reliability evidence for the VAL-ED accumulated in a national field trial. Using data from more than 270 schools across a wide range of settings, we found that the instrument was reliable for measuring principals' learning-centered leadership. Furthermore, there was mostly positive evidence that the VAL-ED distinguished among subscales of principal performance. In conjunction with findings from the VAL-ED development phase, these results support the conclusion that the VAL-ED can be used by K-12 schools to assess learning-centered leadership.