Introduction: Usability of information systems means the ability of these systems to be used effectively, satisfactorily and efficiently for specific objectives by specific users. This study aims to evaluate the usability of hospital information systems (HIS) according to the criteria of isometric 9241, Part 10.Methods: In this cross-sectional study, hospitals which have HIS were identified and the standard questionnaire of isometric 9241, Part 10, was used to assess their HIS. This questionnaire assesses these seven principles: suitability for the tasks, self- descriptiveness, controllability, conformity with user expectations, error tolerance, suitability for individualization, and suitability for learning. The SPSS software was used to analyze data; descriptive tests (mean, percentage and frequency) were used to review the specified criteria.Results: The mean score of suitability for the task was 3.04, while the mean scores for selfdescriptiveness, controllability, error tolerance, and suitability for learning were 2.86, 3.09, 2.95, and 2.97, respectively. The highest score was for conformity with user expectations (3.14) and the lowest was for suitability for individualization (2.57).Conclusion: Developers of HIS in Iran should pay more attention to some abilities such as the ability of forms, screens and menus to be changed according to user’s preferences; compatibility of HIS with user’s level of knowledge and skill; adjustability of the amount of information displayed on screen according to user’s needs; compatibility of the names of commands, objects, and actions with user’s vocabulary; adjustability of input devices according to user’s needs; and adjustability of the software's response times according to user’s speed.