To inform the development of a teacher-oriented movement assessment tool, this study aimed to explore primary school teachers? perceptions of assessing fundamental movement skills (FMS) within physical education (PE) lessons. Thirty-nine primary school teachers of PE, located in the United Kingdom, participated in an individual or group semi-structured interview. Findings signify that teachers perceive a need for an appropriate and effective movement assessment tool that is simple to use, quick to administer, and that provides valuable feedback to guide future teaching and learning. This is vital as teachers indicated that a lack of appropriate resources and a shortage of curriculum time restricts their use of assessment within PE. A movement assessment tool that aligned to the curriculum would be beneficial to teachers to better support children?s learning and acquisition of FMS, as well as to enhance the teachers? own understanding of the process of assessing FMS.