Impulsivity is a personality-based risk factor that has been well studied in relation to risky sexual behavior. Recent conceptualizations of impulsivity have proposed multidimensional facets comprised of premeditation, perseverance, sensation seeking, negative urgency, and positive urgency (UPPS-P model). Prior studies have found that these facets are associated with risky sexual behavior in adolescent and college student samples, but no prior studies have evaluated them in clinical samples. The current study examined how impulsivity-related traits related to two different risky sexual behaviors in a clinical sample of at-risk young adults who had both conduct disorder and substance use disorder symptoms as adolescents (n = 529). Lack of premeditation was also tested as a moderator of the relationship between facets of impulsivity and both risky sex outcomes. Results demonstrated that sensation seeking, negative urgency, and positive urgency were correlated with risky sex behaviors. Additionally, multiple regression analyses indicated that sensation seeking was uniquely associated with the number of sexual partners in the past 5 years, whereas positive urgency was uniquely associated with unprotected sex while under the influence. Finally, a significant interaction between lack of premeditation and negative urgency suggests that at-risk young adults with both high negative urgency and lack of premeditation were the likeliest to have the most sexual partners in the past 5 years. This study adds to the current understanding of the relationship between reward- and affect-driven facets of impulsivity and risky sexual behaviors and may lend utility to the development of interventions for at-risk populations.