Purpose: Fundamental movement skill (FMS) assessors in education environments rely upon real-time FMS assessment; however, the recognition of individual proficiency criteria during real-time process-oriented FMS assessment may be problematic. Few studies consider the accuracy of identifying individual proficiency criteria in process-oriented FMS assessment, even though criteria are relied upon for intervention planning. This study aimed to further understand assessors’ ability to recognize proficiency criteria during real-time FMS assessment and the impact of assessor experience on assessment accuracy. Methods: 10 primary teachers, and 7 pediatric professionals assessed 10 performances of four FMSs (Jump, Hop, Kick, Throw) presented in videos and point-light displays using the Test of Gross Motor Development-2. Results: Accuracy in identifying proficiency criteria was moderate for both pediatric professionals (74.73%) and primary teachers (69.58%), with no differences between groups. In contrast, reliability of overall proficiency scores was good to excellent (ICC>0.8) in both groups. Some individual criteria may be more difficult to assess, evidenced by large average accuracy ranges within skills (e.g., 46% difference between Throw criteria 1 (34%) and 2 (80%)). Conclusions: The study reinforces the difficulty of observing proficiency criteria during real-time FMS assessment regardless of assessor experience. Results suggest that assessors can accurately score overall FMS proficiency, whilst accurate identification of proficiency criteria is problematic. Accurate criterion identification is crucial to understand skill deficiencies and inform subsequent intervention. Attentional demands during real-time assessment may be too great to allow accurate criterion identification, even by experienced assessors, which presents an important consideration for test administrators and developers.