Because the ability to flexibly experience and appropriately express emotions across a range of developmentally relevant contexts is crucial to adaptive functioning, we examined how adolescent attachment security may be related to more functional emotional behavior during a relationship promoting interaction task. Data were collected from 74 early adolescent girls (Mean age 13.45 years; SD = 0.68; 89% Caucasian) and their primary caregiver. Results indicated that, regardless of the parent's interaction behavior and the level of stress in the parent-adolescent relationship, greater adolescent security was associated with more positive and less negative behavioral displays, including greater positivity, greater coherence of verbal content and affect, less embarrassment, and less emotional dysregulation in response to a situational demand for establishing intimacy with the parent. Implications for encouraging and fostering adolescents' capacity to respond to interpersonal contexts in ways that promote the relationship are discussed. (Contains 3 tables.)