Mate poaching occurs when an individual has sexual relations with the romantic partner of another. In Study A, I investigated the prevalence of mate poaching by presenting participants with questions whose devising was informed by a stricter definition of mate poaching than that employed by earlier studies. As expected, relative to participants in earlier studies, the current participants reported fewer experiences of mate poaching. In Study B, I investigated the likelihood that the benefits and costs of mate poaching will, respectively, motivate participants to poach or will deter them from doing so. Results indicated that for males and females to be motivated to poach, the attached individual must be more attractive than the unattached individual.