Infidelity is perhaps the most challenging issue confronting couple therapists and has a high prevalence amongst couples in both clinical and community settings. Despite significant expansion of this field of research in recent years, there has not been a comprehensive review of the literature since 2005. Without such a review, it is problematic for clinicians and researchers to determine best practices and areas needing further inquiry. This article builds on the two most recent reviews (Allen et al., 2005; Blow & Hartnett, 2005) and provides a systematic critical review of the literature on infidelity published in the last 15 years. Key areas of focus include: types of infidelity, its prevalence, its psychological and functional impacts, therapists’ attitudes towards managing infidelity as a clinical issue, empirically supported treatments, and methodological strengths and weaknesses of recent studies. Cultural diversity considerations and therapeutic management of infidelity disclosure are highlighted as particular areas of importance and focus. Additionally, the status of the recent literature was evaluated with respect to the recommendations of past critical reviews, and updated recommendations for future research are provided.