This article examines student teachers' use and perceptions of Twitter, based on a mixed-method comparative approach. Participants (n = 153) were education majors who used Twitter as a part of required coursework in their programs at two universities in Spain and the United States. The theoretical background covers research on international work carried out on Twitter as well as a brief overview of the introduction of technology in two educational national systems. Quantitative data were collected via a survey, while qualitative data were obtained from students' reflective written texts. The majority of participants from both contexts perceived educational benefits to Twitter. However, their use of Twitter, and the nature of their perceptions of its educational value, appeared to differ in important ways. The USA participants' longer and more frequent use of Twitter was accompanied by more positive beliefs regarding the educational relevance of Twitter. While many Spanish participants saw value in the use of Twitter to find and share information, USA students highlighted interactive and collaborative uses. The study uncovers some challenges for learning related to Twitter's short format. in the conclusion section we discuss implications for learning and teaching in an age of ubiquitous social media.