Background: There is limited evidence addressing the impact of adverse childhood experiences (ACEs) on adolescent sexual risk behaviors and pregnancy. In this study, we examined whether individual and cumulative ACEs increased the risk of unhealthy sexual behaviors and adolescent pregnancy. To inform intervention efforts, potential mediating mechanisms focusing on youth developmental assets were examined to explain the association. Methods: Analyses included 88,815 (9th and 11th grade) students who completed the Minnesota Student Survey in the spring of 2016. Results: Adolescents who reported each category of ACEs were more likely to initiate sex, have multiple sex partners, engage in unprotected sex, and be involved in pregnancy. Different youth assets, included self-regulation skills, connectedness to school, not skipping school, and academic performance, were associated with lower likelihood of sexual initiation and sexual risk-taking. They served as important mediators to reduce, though not completely diminish, the adverse effects of ACEs on sexual initiation and adolescent pregnancy. Conclusions: The results suggest that the relationship between ACEs and adolescent sexual risk behaviors and pregnancy is strong and graded. Effective school initiatives and intervention efforts should encourage the development of self-regulation and connectedness to school among teens who had been exposed to ACEs.