Introduction: Musculoskeletal Disorders (MSDs) are among the most common occupational diseases, and ergonomics and occupational health engineering specialists need reliable and valid methods for assessing high-risk activities and the factors contributing to their occurrence. Materials and Methods: In this cross-sectional study, 100 nurses employed at Namazi Hospital in Shiraz were randomly selected. Data was collected using a demographic/occupational questionnaire, Hierarchical Task Analysis (HTA), and the Ergonomics Screening and Prioritizing Tool (ESPT). Three observers simultaneously assessed the risk of developing MSDs for each job duty. After a six-month interval, the same observers re-evaluated the same group of nurses in the same work Postures. To assess the reliability of ESPT between and within observers, the Intra-class Correlation Coefficient (ICC) and the Kappa Multi-rater Fleiss method were used. Data analysis was conducted using SPSS software version 26. Results: The results of the study showed a high agreement between each observer as well as between the three observers before and after six months. The ICC for observers 1, 2, and 3 were respectively 0.951, 0.947, and 0.927, and also between each of the three observers for the first and second time respectively 0.955 and 0.941. Conclusion: The ESPT has been shown to possess high reliability for assessing the risk of developing MSDs among nurses, and it can be used for this purpose.