Participation in the workplace has been proposed as a potential structural-level HIV/STI prevention strategy for youth. Only a few cross-sectional studies have explored the effect of work during adolescence and young adulthood on sexual behavior and their results have been mixed. This study builds on this literature by exploring whether work influences youths’ sexual behavior in a cohort of African American youth [N = 562; 45% males; M = 14.5 years, SD = 0.6] followed from adolescence to young adulthood (ages 13 to 25). Using growth curve modeling, we tested whether working was associated with older sex partners. Then, we explored the association between sex partner age differences and sexual behaviors (i.e., number of sex partners, condom use, and frequency of sexual intercourse). Finally, we tested whether the relationship between sex partner age differences and sexual behaviors was confounded by working. Working greater number of hours was not significantly associated with having older sex partners. Sex partner age differences was associated with number of partners, condom use, and and higher sex frequency. These associations were larger for females. Working was associated with higher sex frequency, after accounting for age differences. We discuss the implications of these findings for future research and program planning, particularly in the context of youth development programs.