Purpose – The paper aims to present a critical review on the adoption and use of Twitter in libraries. Twitter, a microblogging service, is becoming more and more popular among libraries as a means of reaching users and as a marketing tool for their services. Design/methodology/approach – The method of systematic review is used to identify, collect and critically present all relevant literature. Papers’ aims were analyzed to identify the emergent themes and sub-themes in an effort to gain a better understanding of libraries’ use of Twitter. Findings – A systematic and critical analysis of the literature revealed the specific reasons why a library should adopt Twitter; the specific examples and thoughts on how Twitter could be used to promote libraries’ interests; the different ways Twitter had affected diverse aspects and functionalities of libraries; and the attempts to provide guidelines for librarians. Research limitations/implications – This literature review has implications for research in that libraries could explore the way public view their presence on social networking sites such as Twitter to better gain from it. In addition, it indicates what libraries should expect when they adopt Twitter. This study reviews only papers published between 2007 and 2013 in the English language. Originality/value – This paper contributes in identifying, collecting, analyzing and critically presenting published research referring to the adoption of Twitter in the field of Library Science. In addition, it identifies and discusses the main issues librarians and libraries need to consider, when faced with the challenge of adopting Twitter.