Given that adolescence is a critical period for socioemotional development, marked by shifting dynamics in the parent-child relationship, parent-adolescent dyadic regulation may serve as a key mechanism linking the quality of the parent-adolescent relationship to adolescent mental health. The current study investigated two dyadic regulatory processes during mother-adolescent conflictual interactions as interpersonal mechanisms underlying the link between adolescent-mother attachment security and adolescents' internalizing and externalizing symptoms: (a) mutual engagement in positive affect (i.e., dyadic positivity) and (b) mutual engagement in re-coordination following relational mismatches (i.e., dyadic repair). Eighty-six adolescents (M