Purpose: This article examines characteristics of the external environment of library and information centres of Islamic Azad University in Iran, focusing on perceived environmental uncertainty and perceived source accessibility and quality, and their impacts on the amount of scanning and the frequency of information source use. Methods: This research surveyed the library managers of ninety-four units of Islamic Azad University. Data were collected by a mail questionnaire with a response rate of 90.42%. Findings: Results show that there is a positive correlation between respondents' perceived environmental uncertainty and the amount of scanning. Additionally, perceived source accessibility and quality are associated more with frequency of information source use in environmental scanning than with perceived environmental uncertainty; and managers mostly rely on personal and internal information sources. Conclusion: This research shows that: libraries as organizations are sensitive to their external environments, and variable, complex and important events occurred in it; managers of academic libraries feel uncertainty and complexity in their decision making and rely on information sources; and the use of library and electronic information services as information source in environmental scanning ranked in a high level compared to other sources.