Very likely due to its modest nature, the Cosa Mithraeum has been mentioned in scholarly publications only four times – each in passing – since its discovery in 1954. This sparse attention, restricted solely to literature on Cosa, has meant that the mithraeum is well-known among those intimately familiar with the colony, but has languished in complete obscurity among Mithraic scholars for the past half century. In addition to bringing the Cosa Mithraeum to the attention of a wider audience, this article also argues for a re-evaluation of the most recent dating of the mithraeum. Recent advances in scholarship on mithraea at Ostia give ample reason to suggest that the original date for the Cosa Mithraeum might be more accurate than later interpreters have assumed. Furthermore, the ongoing excavations of Cosa's bath complex, conducted by Florida State University, Bryn Mawr College, and Tübingen University have revealed a city that was still quite active during the 2nd century CE. In light of these developments, this article is an overdue study of the Cosa Mithraeum and its role in the history of the colony.