Emotional variability reflects the ability to flexibly switch among a broad range of positive and negative emotions from moment-to-moment during interactions. Emotional variability during mother-adolescent conflict interactions is considered to be important for healthy socio-emotional functioning of mothers and adolescents. The current observational study examined whether dyadic emotional variability, maternal emotional variability, and adolescent emotional variability during conflict interactions in early adolescence predicted mothers’ and adolescents’ internalizing problems five years later. We used data from 92 mother-adolescent dyads (Mage T1 = 13.05; 65.20 % boys) who were videotaped at T1 while discussing a conflict. Emotional variability was derived from these conflict interactions and it was observed for mother-adolescent dyads, mothers and adolescents separately. Mothers and adolescents also completed questionnaires in early adolescence (T1) and five years later in late adolescence (T6) on mothers’ internalizing problems, and adolescents’ anxiety and depressive symptoms. Hierarchical regression analyses showed that less dyadic emotional variability in early adolescence predicted relative increases in mothers’ internalizing problems, adolescents’ depressive symptoms, and adolescents’ anxiety symptoms from early to late adolescence. Less maternal emotional variability only predicted relative increases in adolescents’ anxiety symptoms over time. The emotional valence (e.g., types of emotions expressed) of conflict interactions did not moderate the results. Taken together, findings highlighted the importance of considering limited emotional variability during conflict interactions in the development, prevention, and treatment of internalizing problems of mothers and adolescents.