Native Americans in the United States are not typically regarded as a most at-risk population for HIV or other sexually transmitted infections (STIs), despite emerging evidence which suggests otherwise. As a result, Native Americans lack access to key prevention services and programs. In planning prevention programs for this unique population, however, it is important to take into account the cultural factors that may be implicated in health risk behaviors. Historical Loss is a type of historical trauma that has been reported in Native Americans, and which may be related to health behaviors. We examined whether Historical Loss was associated with sexual risk behaviors in a sample of 120 American Indian men living in Fort Peck Reservation in northeastern Montana who completed questions regarding Historical Loss and sexual risk behaviors. Symptoms of Historical Loss that reflected Anxiety/Depression and Anger/Avoidance were associated with an increased likelihood of individuals' having sex with multiple concurrent partners. Health interventions that aim to address HIV/STI prevention should take symptoms of Historical Loss into account, as Historical Loss could be a potential factor that will mitigate HIV, STI, and pregnancy prevention efforts in this population.