Purpose-The present study aims to investigate levels of awareness and use of Web 2.0 tools by librarians in the university libraries of East Azerbaijan (EA) in Iran and to determine how librarians use these tools in everyday life. Design/methodology/approach-A Web-based questionnaire was used to collect data from 38 per cent librarians in the university libraries of EA. Findings-The research findings indicate that the librarians were more familiar with Web 2.0 tools such as wikis and blogs. While librarians widely use blogs and wikis, tools such as social bookmarking, social networks, RSS feeds, instant messaging and digital maps were less frequently used. Results obtained from present study indicated that librarians use Web 2.0 tools mostly to communicate with friends and family, to keep up-to-date, to collaborate with colleagues and for curiosity and fun. Also, librarians believe that Web 2.0 tools can be used mostly for sharing information about library resources. Internet filtering, lack of access to high-speed internet and lack of training were the major obstacles for Web 2.0 adoption by librarians. Originality/value-This study is a useful source for implementing Web 2.0-based technology in libraries. Also, this study will help managers understand the librarians' needs about Web 2.0 to improve their library services.