American Indian youth and emerging adults are disproportionately susceptible to risky sexual behavior. Several studies have examined the relationship between American Indians and sexually transmitted infections (STIs) by examining sexual risk behaviors. However, few studies have explored sexual risk behaviors through the lens of attachment theory. Therefore, the purpose of this study was to examine the association between sexual risk behaviors and attachment style among American Indian emerging adults who were raised in stepfamilies. A structural equation model was used to examine the relationship between the latent variables, anxious and avoidant attachment style, and the dependent variable of sexual risk behavior. This study found a significant association between sexual risk behaviors and (a) anxious attachment style, (b) income, and (c) gender. This study yields important findings about the nature of sexual risk behavior and STI development among American Indians raised in stepfamilies and prompts further study into the development of attachment relationships and additional considerations that may influence sexual risk behavior among this population.