Adolescence is considered to be a sensitive time in the lifespan. Social experiences that occur during this time contribute to one’s sense of self and belonging within the peer group, which has important implications for later outcomes. Positive peer interactions can function as an antidote to internalizing symptoms (e.g., anxiety, depressed affect) by providing security- and intimacy-based experiences, whereas negative experiences (e.g., being disliked, excluded) are known to have unfavourable consequences on development. The aim of this project was to investigate the relationship between specific friendship features and experiences that occur across contexts (dyadic, classroom) and emotional adjustment in a sample of adolescents. This was achieved by conducting three longitudinal studies using self-report and sociometric data collected from fifth and sixth grade students in Montréal, Canada and Barranquilla, Colombia. The results of Study 1 provided support for the use of a measurement burst design methodology to account for momentary deviations in self-reported internalizing symptomology. Specifically, the burst design was found to provide a more stable and reliable measure of anxiety compared to traditional single-time longitudinal measurement designs. Study 2 assessed the degree to which perceived friendship quality (security, intimacy) and various classroom-level features (e.g., individualism, collectivism, acceptance/density, SES) minimize the continuity of social anxiety among youth. Support was found for the protective function of friendship security on anxiety, and classroom-levels of individualism and acceptance/density were found to strengthen the negative effect of security across the school year. Intimacy was also found to be an important source of emotion regulation for lower SES groups and groups that are highly individualistic. Study 3 employed the benefits of a burst design to investigate how depressed affect influences accurate awareness of youth’s level of acceptance among their peer group. Findings suggested that higher levels of depressed affect make early adolescents insensitive to actual levels of social acceptance from their peers, despite the fact that it may be objectively higher. Together, these studies improve our understanding of how important features of friendship quality contribute to adolescents’ well-being, as well as how negative peer experiences and depressed affect function together to influence self-perceptions.