["Journal of Personality, EarlyView. ", "\nABSTRACT\n\nObjective\nEmpirical evidence suggests that perfectionism significantly influences emotion regulation; however, longitudinal data on this relation is still scarce. Hence, the current three‐wave longitudinal study's purpose was to investigate the interplay between perfectionism and emotion regulation both at the group level, as well as at the within‐person level, in an adolescent sample.\n\n\nMethod\nThe total sample comprised 454 adolescents (69% girls) aged 10–18 years. Adolescents from five public schools completed a paper‐pencil questionnaire over three consecutive school semesters.\n\n\nResults\nAt the group‐level, cross‐lagged panel analyses showed a unidirectional longitudinal relation between perfectionistic strivings and reappraisal and bidirectional longitudinal relations between perfectionistic concerns and suppression. Conversely, at the within‐person level, random‐intercept cross‐lagged panel analyses showed non‐significant longitudinal relations.\n\n\nConclusions\nInsights into how perfectionism influences the development and maintenance of emotion regulation strategies in adolescence, as well as their bidirectional relation, are discussed.\n\n"]