The aim of the present study was to investigate the information needs of physicians and residents during the clinical decision-making. The research has been performed with phenomenological approach and using semi-structured interview based on critical incident technique with 28 physicians and residents of the educational health care centers of Birjand city South Khorasan province, Iran. The results showed that the information needs of physicians and residents were mostly related to diseases, diagnosis, prescription, treatment, disease follow-up, learning and self-updating, education and research. The information sources utilized were categorized into three main themes of human sources, electronic sources and print sources. The barriers against their information seeking were personal, organizational, technological, skill related, nature of information seeking, and barriers related to information sources. The present study provides a clear picture of the information needs, the information resources and the barriers to finding information for physicians and residents, therefore, the results of the present study can help medical libraries to improve their collection of resources and services to support the information needs of physicians and residents. It also paves the way for designers of information systems in creating systems that suit the needs of physicians in every stage of clinical decision-making and helps libraries in solving the challenges of finding information for physicians.