This study was designed to examine secondary teachers' use of evaluative language resources in their qualitative written feedback on student work and factors shaping the deployment of such resources. Drawing on appraisal theory as an analytic framework for the language of evaluation, the study analyzed 84 teachers' evaluative reports on their students' research projects. The teachers' use of several types of evaluative language was found to differ along the lines of disciplinary background and teaching experience. These results can be explained by disciplinarily valued dispositions, epistemological beliefs, knowledge-making practices, and varying knowledge of (in)effective feedback resulting from cumulative teaching experience. Implications are derived from these findings for developing teachers' competence in using evaluative language effectively to provide feedback that can support and maximize students' learning.