Emotion regulation has traditionally been conceptualized as an intrapersonal phenomenon with a focus on individuals’ personal experiences (e.g., feelings) and behaviors. However, a relational perspective on emotions underscores that emotion regulation occurs predominantly in the context of social interactions. Close relationships play an important role in emotion regulation in social interactions, particularly during emerging adulthood when individuals spend more time outside the family home. However, few studies have examined predictors of the use of different emotion regulation strategies in everyday life. Using Ecological Momentary Assessment, we first examined concurrent associations between social contexts (closeness to interaction partner and pleasantness of interaction) and use of emotion regulation strategies (cognitive reappraisal and expressive suppression). Second, we used lagged models to explore potential bidirectional associations between aspects of the social context and emotion regulation strategy use. We collected EMA data four times per day for two weeks, resulting in 3,158 momentary assessments. Better quality of social interactions was associated with both less suppression and less reappraisal at the same moment, but not at subsequent moments. Interestingly, we found that reappraisal at one moment predicted more pleasant interactions and closeness at the next moment. Our findings underscore the importance of understanding both social contexts and emotion regulation on momentary levels. This study holds implications for understanding social context and emotion regulation in the everyday lives of emerging adults.