This longitudinal study examined person-environment interplay by testing interaction effects between adolescent personality type (i.e., overcontrollers, undercontrollers, and resilients) and young adult romantic relationship quality on young adult delinquency and anxiety. The study employed six waves of longitudinal questionnaire data collected across ten years from Dutch youths. Results showed that support from romantic partner was related to a relatively stronger decrease in anxiety in young adulthood for overcontrollers than for resilients. Moreover, higher negative interaction with romantic partner was related to a relative increase in delinquent behaviors for undercontrollers, while no such links emerged for overcontrollers and resilients. This study highlights the importance of considering the interplay between personality characteristics and environmental-relational factors when examining young adults’ developmental outcomes.