This study examined the prospective influence of adolescent working memory (WM) on changes in impulsivity and sexual risk taking and assessed whether this relation could be explained by confounding effects of parental influences. Data from 360 community adolescents (Mage = 13.5 ± 0.95 years; 52% female; 56% non-Hispanic White; low-mid socioeconomic status (SES); recruited from Philadelphia area in 2004–2005) were analyzed using structural equation modeling to predict changes in impulsivity and sexual risk taking over a 2-year follow-up, using baseline assessments of WM, parental monitoring, parental involvement, and SES. Stronger WM predicted reduced involvement in sexual risk taking at follow-up, effects channeled through changes in impulsivity dimensions of “acting without thinking” and “inability to delay gratification.” Parental variables had a protective influence on adolescent impulsivity and risk involvement, but the effects of WM operated independently of parental influences.