Growing interest in online learning has instructors looking for new ways to engage learners in asynchronous discussions. Building on experiences with hashtag use to connect on social media platforms, the purpose of this study is to investigate the contexts of hashtag use and its associated impact on learner engagement in asynchronous online discussions. In more detail, this mixed-methods case study will answer the following questions: 1) How and in what context do students use hashtags in online discussions? and 2) In what ways, if any, does the use of hashtags promote engagement in an online community? Findings suggest that while classifying and organizing course information was a strong motivator for tagging posts, hashtags were also used to connect to others in the learning community, express opinions, and encourage knowledge building. The results from our study contribute to a better understanding of engagement with and through hashtag use.