Purpose: Four entrustable professional activities (EPAs) were developed by the Taiwan Society of Emergency Medicine (TSEM) and evaluated in pilot programs for postgraduate year (PGY) trainees in their emergency medicine (EM) rotations in Taiwan in recent years. However, no validation results of the abovementioned EPA-based assessments have been reported. This study aimed to evaluate how the EPAs work in the context of postgraduate training in Taiwan. Methods: From August 2018 to February 2022, in their EM rotations, 112 PGY trainees in a teaching hospital in northern Taiwan underwent ad hoc EPA-based assessments of the four EPAs that had been performed in the EM. The entrustment levels of these EPAs were collected and examined through a series of psychometric tests. Results: Four EPAs and their 19 sub-EPAs were examined and showed excellent internal consistency (alpha: 0.870-0.936). Exploratory factor analyses revealed that all EPAs, except EPA 1, retained only one factor. In the first factor of EPA 1, the factor loadings of all eight sub-EPAs are positive. In the second factor, the factor loadings of two sub-EPAs are higher than 0.4, which indicates that the second factor measures other types of clinical competence, such as communication skills. Conclusions: The four EPAs developed by TSEM can be a valuable tool to assess clinical competencies of PGY trainees in EM rotations. However, EPA 1 measures more than one dimension of clinical competence. Low entrustment levels in this EPA-based assessment may suggest the need for training that is tailored to communication skills.