Introduction: Quality improvement is the main purpose of health care organizations in general and of hospitals in particular. Physicians are the main users of information systems. It is, therefore, necessary to study the impact of using medical information systems on health care quality and the factors affecting the physicians’ use of these systems.

Methods: This is a descriptive-analytic study in which simple randomized sampling was used to select 74 physicians in teaching hospitals. The reliability of a researcher-made questionnaire – validated by experts – was confirmed by test-retest. The data were analyzed by SPSS using descriptive and inferential statistics.

Results: Laboratory information system, online vital sign system, and drug interaction inspection system (with mean values of 4.61, 4.28, and 4.08, respectively) showed the highest effects on health care quality. Moreover, the factors of data security concern, constant system upgrade, and lack of trust in the quality of the services of information technology workforce (with mean values of 4.05, 4.04, and 3.97, respectively) were found to have the highest impact on the physicians’ use of medical information systems.

Discussion: Physicians stated that information systems had an effective role in the quality improvement of health care. Data security concerns, lack of computer skills, lack of training for the optimal use of information systems, and slow transmission speed were the most effective factors in preventing physicians from using information systems. Thus, optimization of information systems especially in the aforementioned areas seems necessary for health care quality improvement.