The purpose of this study is to identify the types of cognitive biases in the process of information retrieval. This research used a mixed-method approach for data collection. The research population consisted of 25 information retrieval specialists and 30 post-graduate students. We employed three tools for collecting data, including a checklist, log files and semi-structured interviews. The findings showed that from the perspective of information retrieval specialists, the cognitive biases such as ‘Familiarity’, ‘Anchoring’, ‘Rush to solve’ and ‘Curse of knowledge’ could be of the greatest importance in the field of information retrieval. Also, in terms of users’ searching, the ‘Rush to solve problems’ and ‘Mere exposure effects’ biases have the highest frequency, and the ‘Outcome’ and ‘Curse of knowledge’ biases have the lowest frequency in the process of user retrieval information. It can be concluded that, because cognitive biases occurring in information retrieval, designers of information retrieval systems and librarians should pay attention to this issue in designing and evaluating information systems.