["Journal of Child Psychology and Psychiatry, EarlyView. ", "\n\nBackground\nAdolescence, particularly for girls, is a period of heightened risk for depressive symptoms and increased interpersonal stress. Although depressive symptoms and interpersonal problems are known to co‐occur, prior work has predominantly examined between‐person associations, leaving within‐person processes unclear. This study addressed this gap by testing longitudinal within‐person associations between depressive symptoms and interpersonal problems in adolescent girls over 4 years, evaluating whether links were reciprocal or unidirectional.\n\n\nMethods\nParticipants included 543 adolescent girls from the Pittsburgh Girls Study. Across four waves (mean ages = 16.5–19.3 years), girls self‐reported depressive symptoms and eight types of interpersonal problems: domineering, vindictive, cold, socially avoidant, nonassertive, exploitable, overly nurturant, and intrusive. For each interpersonal problem, we fit both constrained and unconstrained random intercept cross‐lagged panel models and selected the constrained model unless it demonstrated a significantly poorer fit than the unconstrained model, prioritizing parsimony.\n\n\nResults\nThe selected models demonstrated good fit for all eight interpersonal problems. Within‐person increases in depressive symptoms predicted subsequent within‐person increases in overly nurturant and socially avoidant problems, whereas these interpersonal problems did not predict subsequent within‐person increases in depressive symptoms. By contrast, depressive symptoms and domineering problems reciprocally predicted one another over time.\n\n\nConclusions\nThis study clarifies how depressive symptoms and interpersonal problems influence one another over time within individuals in adolescent girls. Findings highlight domineering problems as a potential intervention target for breaking cycles of mutual reinforcement with depressive symptoms. Moreover, addressing depressive symptoms may yield social benefits by reducing subsequent overly nurturant and socially avoidant problems.\n\n"]