This study examines the validity of a student teaching evaluation instrument used in a teacher preparation program. Grounded in research-based conceptualizations of teaching and aligned to standards from relevant professional associations, the instrument is used to evaluate teacher candidates during their student teaching experience. To determine the instrument's validity, we used exploratory factor analysis and structural equation modeling to study responses from cooperating teachers, university supervisors, and student teachers. Findings partially confirm the validity of the instrument and indicate that the 30 competencies of the instrument comprise an invariant structure of four domains: planning, onstage teaching, assessment, and professionalism. Implications include instrument revision, the need for rater training, and further exploration of curricular alignment.