ObjectiveTo examine the relationship between reproductive attitude of friends during adolescence, and unintended pregnancy outcomes and contraceptive non-use during early adulthood. Study DesignWe used longitudinal data from the National Longitudinal Study of Adolescent to Adult Health (n = 1866). Adolescent friendship network structures were constructed from the first wave of data to assess reproductive attitudes of friends, measured via 3 subscales: attitude toward contraceptive use, attitude toward sex in adolescence, and attitude toward pregnancy in adolescence. We then used multilevel logistic regression to examine the relationship of friends’ reproductive attitudes in adolescence with unintended pregnancy and contraceptive non-use in adulthood. ResultsAround one-third of the sample experienced at least one unintended pregnancy, and 12% reported contraceptive non-use. Being friends with individuals who are not accepting of adolescent pregnancy reduced the likelihood of an unintended pregnancy in young adulthood (adjusted odds ratios [aOR]: 0.79; 95% CI: 0.67–0.94); this association varied by sex, being significant only for females (aOR:0.75; 95% CI: 0.58–0.96). Additionally, friends’ acceptability of adolescent sex increased the odds of contraceptive use in later life. Individuals with friends who held negative attitude toward contraceptive use during adolescence were more likely to be non-users in later life (aOR:1.37; 95% CI: 1.03–1.81). ConclusionsOur results suggest a relationship between adolescent social networks and reproductive health outcomes in young adulthood, highlighting the importance of friendship networks for young individuals’ reproductive well-being. ImplicationsAttitudes held by adolescent friends regarding contraceptive use, adolescent sex, and adolescent pregnancy have significant, and distinct associations with an individuals’ later-life reproductive health outcomes. Future research should consider evaluation of social network-based sexual and reproductive health interventions aimed at adolescents.