Purpose: Although there has been increasing optimism about the potential for social media platforms such as Twitter to support educators' professional learning, it is yet unclear whether such promises hold true. Accordingly, the purpose of this paper is to explore school administrators' use of Twitter for professional learning. Design/methodology/approach: This qualitative case study draws data collected from 17 school administrators from throughout the USA and Canada. In addition to individual, semi-structured interviews, administrators' tweets were collected for two weeks. This resulted in 1,460 tweets. Analyses were aimed at perceptions about Twitter, the knowledge shared, and its impact on practice. Findings: Findings presented a paradox: although administrators were enthusiastic about the social and professional benefits associated with Twitter, they did not share or apply much knowledge commonly associated with administrator work. Topically, administrators' tweets tended to focus on technology, rather than other leadership issues. Also, administrators' informal tweets focussed on norms and relationships in the online community, rather than other dimensions to leadership craft. What's more, leaders were rarely able to point to direct changes in their school policies or practices resulting from Twitter. Research limitations/implications: The present study raises issues for future research, including: how do administrators evaluate the expertise of peers or other resources online? How do leaders negotiate conflict or dialogue online? How might leaders leverage social media as public relations tools? Practical implications: Whereas popular media have described the benefits of platforms like Twitter in broad strokes, the present study provides a detailed account of the practitioner experience. This account includes not only descriptions of what leaders might (or might not) be learning via Twitter, but also some of the benefits of being able to socialize with colleagues online. Originality/value: As social media use has grown, so has interest in using such platforms for professional learning. However, there is a gap in knowledge regarding the strengths and shortfalls facing administrators. This study breaks new ground by comparing Twitter's purported benefits to user's tweets and outcomes.