Posttraumatic stress disorder (PTSD) is associated with impairments in relationship functioning. Beyond the abundance of research that has demonstrated this basic link, more recent research has begun to explore possible mediators and moderators of this association. The present paper reviews and synthesizes existing literature in the context of an overarching organizational framework of potential ways in which PTSD impacts relationship functioning. The framework organizes findings in terms of specific elements of PTSD and comorbid conditions, mediators (factors that are posited to explain or account for the association), and moderators (factors that are posited to alter the strength of the association). Specific symptoms of PTSD, comorbid symptoms, and many of the potential mediators explored have extensive overlap, raising questions of possible tautology and redundancy in findings. Some findings suggest that non-specific symptoms, such as depression or anger, account for more variance in relationship impairments than trauma-specific symptoms, such as re-experiencing. Moderators, which are characterized as individual, relational, or environmental in nature, have been the subject of far less research in comparison to other factors. Recommendations for future research and clinical implications of the findings reviewed are also presented.