Emotion-related socialization behaviors that occur during parent-child interactions are dynamic. According to Eisenberg, Cumberland, and Spinrad's (1998) model, ongoing parental reactions to emotions and discussions of emotion indirectly shape children's socioemotional competence throughout childhood and adolescence. Typically-developing adolescents-girls especially-are at increased risk for developing internalizing symptoms. We examined if and how emotion dynamics of mother-daughter interactions contribute to adolescent girls' internalizing symptoms. We applied grid-sequence analysis (Brinberg et al., 2017) to observational data obtained while N = 96 typically-developing adolescent girls (Mage = 13.99 years) and their mothers engaged in five different emotionally-laden discussions. We identified patterns of expressed emotions that unfolded during each discussion and examined how interdyad differences in those patterns were associated with mothers' and daughters' internalizing symptoms. Dyads differed with respect to whether mothers or daughters tended to regulate positive emotion expressions. Interdyad differences in moment-to-moment dynamics of happy/excited and worried/sad discussions were associated with adolescent girls' social anxiety symptoms, while differences in emotion dynamics of proud, frustrated/ annoyed, and grateful discussions were not. Taken together, results illustrate how methodological innovations are enabling new examination and detailed description of parent-child emotion socialization dynamics.