This research focuses on the assessment literacy, that is, the understandings of assessment terminologies and how they relate to each other, in academic staff developers in the UK, collected via questionnaires and semi-structured interviews. Academic staff developers have been trained and certified to support new higher education lecturers in learning,teaching, and assessment practices, and provide continuing professional development for more experienced staff. Results showed inconsistent and differing understandings between and within individuals. These inconsistencies may reflect the lack of consistency of terminology in the literature. This lack of common understanding has far-reaching implications and needs reconciling to enhance personal and collective assessment literacies, particularly since our respondents have responsibility for training the next generation of academics.