Attachment state of mind was investigated as a long‐term predictor of romantic relationship competence. A secure early adolescent attachment state of mind was hypothesized to predict more constructive dyadic behaviors during conflict discussions and support‐seeking interactions in late adolescence and early adulthood. Utilizing multimethod data from a community sample of 184 individuals, followed from ages 14 to 21, adolescents with a secure attachment state of mind at age 14 were found to be in relationships that displayed more constructive dyadic conflict discussion behaviors and dyadic supportive behaviors at both ages 18 and 21. Results suggest substantial links between early adolescent attachment state of mind and the adult romantic relationship atmosphere an individual creates and experiences.