Firearms research has been hindered by a persistent lack of high-quality, reliable, and timely data. Using social media data in firearms research is, therefore, appealing: these data are large in scale, continuously provided, passively obtained, inexpensive in some cases, and easily combined with data from traditional sources. We consider how social media data have been used in firearms research to date and how they can be best used moving forward. Despite the many advantages of using social media data, there are key analytical and ethical considerations associated with their use, including understanding the underlying population, constructing valid and reliable measures from shared content, the possibility of false data and misinformation through fake accounts, and concerns having to do with the privacy and consent of social media users. Notwithstanding these drawbacks, we show that there is a compelling case for the continued development of these data for firearms research and suggest principles for their responsible use in this context.