Aims: Adolescents have heterogeneous patterns of marijuana use, the most common pattern being intermittent or occasional use. Youth who use marijuana are at risk of escalating and problem use. Adolescents may change their romantic partners more frequently than their non-romantic peers. Partner change may explain adolescents intermittent marijuana use. We examined: (1) whether having a marijuana using romantic partner predicts marijuana use among adolescent females, and (2) if feelings of intimacy for the partner is associated with marijuana use concordance. Methods: A cohort of adolescent females (N = 122), aged 1619 at baseline, recruited from health clinics or community venues, completed quarterly interviews for 18 months. At each interview, participants reported on their past 3 month marijuana use and their partners marijuana use. Participants reported their feelings of closeness and trust for their current main partner. Concordance was both use or neither use. Random-intercept logistic regression was used to estimate subject-speciﬁc effects. Results: Seventy-ﬁve percent of participants who reported any marijuana use had periods of use and no use over the study followup. A participant was more than twice as likely to report using marijuana when her current partner used marijuana compared to when she had a non-marijuana using partner (OR: 2.33, 95%CI: 1.27, 4.27). Participants who reported high feelings of intimacy for their partner were 47% more likely to be concordant on marijuana use with that partner (OR: 1.47, 95%CI: 1.004, 2.16). Conclusions: It is developmentally appropriate for adolescents to move toward intimate relationships. Romantic partners are different from non-romantic peers in unique and signiﬁcant ways, particularly the level of emotional intimacy achieved in the relationship. Results suggest that strong feelings of intimacy for a partner may pose a unique context for risk.