ObjectivesAs the largest group providing healthcare services, nurses require well-designed information systems in their practice. This study aims to evaluate the usability of nursing information systems (NIS).MethodsThis cross-sectional survey was conducted in 2015. The settings of the study consisted of four hospitals affiliated with three medical universities in Tehran (Iran). The subjects of the study included nurses who had access to and used a NIS developed by four major software companies. The data were collected using a modified version of a usability questionnaire known as IsoMetrics, based on the International Standard ISO 9241, Part 11. The questionnaire is composed of 35 questions divided into seven general criteria. The validity of the questionnaire was determined by experts in the field, and the reliability was checked using Cronbach's alpha (α = 0.91). The questionnaire was then distributed to 184 nurses.ResultsThe response rate was 64.6%. Among the seven ISO usability criteria, suitability for the task (3.10 ± 1.24) and suitability for learning (3.10 ± 1.27) had the highest mean value. The lowest mean value (2.37 ± 1.29) was related to the suitability for individualization.ConclusionsAddressing issues related to individualization and self-descriptiveness could improve the usability of nursing systems. Considering usability requirements in the design of a NIS will lead to the efficient and effective use of these systems.