Strong child support enforcement requires fathers to take financial responsibility for their children and may also encourage more responsible sexual behavior. Using the 1997-2001 waves of the 1997 National Longitudinal Survey of Youth (N = 4,272), this article examines the association between child support enforcement and the sexual activity of male adolescents. Stronger child support enforcement was associated with fewer sexual partners, less frequent sexual intercourse, and a higher likelihood of using contraceptive methods among adolescents who had had sexual intercourse in the 12 months preceding data collection. The effects of child support enforcement were particularly strong for non-White adolescents and those living in high-poverty areas. These findings suggest that strengthening child support enforcement may be associated with reductions in some aspects of male adolescents' sexual activity.