Whereas theory and research agree that social interactions are central mediators of the associations between personality and relationship outcomes, less is known about the mechanisms involved. This is particularly evident when looking at adolescence, when social networks restructure and expand. Drawing on experience sampling data from two adolescent samples (overall N > 200), we examined which self and other perceptions of real-life social interaction behaviors contribute to the links between personality (i.e., extraversion, agreeableness, and neuroticism) and momentary satisfaction with social interactions. Multilevel exploratory factor analyses revealed that most social perceptions could be represented by two factors, labeled expressive and communal behavior. As hypothesized, we found that higher extraversion and agreeableness, and lower neuroticism predicted greater satisfaction with social interactions. These associations were mediated by higher perceptions of expressive and communal behavior in the case of agreeableness and extraversion and by lower perceptions of expressive behavior in the case of neuroticism. Contrary to our expectations, the results were the same no matter whether self or other perceptions were used as mediators. We discuss how our results inform about the co-development of personality and social relationships from a microlevel perspective and outline directions for future research on perceived social interaction behavior.