This study sought to develop and validate a classroom-based language assessment literacy scale to measure teachers' perceived classroom-based assessment knowledge and practice. Exploratory factor analysis revealed that the scale items clustered around four factors: (a) purposes of assessment and grading, (b) assessment ethics, (c) student involvement in assessment, and (d) feedback and assessment interpretation. Moreover, the scale was administered to 348 Iranian English as a foreign language teachers. The findings showed that the majority reported to be literate in classroom-based language assessment and agreed to the allocation of more space to classroom-based language assessment in teacher education courses. The findings suggest that the newly-developed scale can serve as a valid and reliable tool to explore language teachers' classroom-based assessment literacy.