This paper argues that Benjamin Keach’s view of the mystical union and communication of attributes between believers and Christ is theologically consistent with the teaching of the church fathers. Benjamin Keach (1640-1704) was ardently opposed to the Christological heresies that had become prevalent during his life. Groups such as the Caffynites and the Quakers, a sect of which his daughter, Hannah, would become a member, distorted the church’s teaching on the hypostatic union, causing damage to the foundational doctrines of the church. Keach argued that the union of Christ’s two natures was directly related to the mystical union a believer has with Christ, a union that is not only primary, but also essential for salvation. A result of the mystical union a believer has with Christ is the communication of attributes. Such teaching was not unfamiliar to scholars contemporary to Keach, but his emphasis on union, the communication of attributes, and the similarity his teaching had with the church fathers in his writings is significant and worth considering. Therefore, after presenting a biographical sketch of Benjamin Keach that provides historical context to the development of his theology, the Caffynites and Quakers teaching on the hypostatic union are examined along with Keach’s charge against them and their impact on believers. Communication of attributes is then defined, and Athanasius is presented as an example of how the church fathers discussed the mystical union of a believer and Christ as well as the communication of attributes that results. John Owen’s teaching on union and communication of attributes demonstrates Keach’s consistency with scholars of his era and helps provide a link back to the church fathers. Finally, Keach’s own writings on these doctrines are surveyed, demonstrating that his teachings were consistent with that of the church fathers.