Emotion regulation is foundational to children's psychological wellbeing and future school adjustment. As young children are spending increasing amounts of time in preschool programs, investigating how early childhood classrooms can foster emotion regulation development is warranted. In this study, we tested individual children's interactions with teachers and peers as potential mechanisms through which inhibitory control supports emotion regulation in the preschool classroom. Participants included 767 preschool children (49% female; M = 4.39 years old, SD = .08) from low-income households (income-to-needs ratio M = 1.45, SD = 1.06). Fifty percent of children were Black, 22% White, 13% Latino, and 15% Other race/ethnicity. Children completed direct assessments of inhibitory control in the fall, teachers reported on children's emotion regulation in the fall and spring of the preschool year, and trained observers rated the quality of individual children's interactions with teachers and peers in the fall, winter, and spring. Accounting for earlier emotion regulation, mediation analyses indicated that children's inhibitory control operates through individual children's (a) positive interactions with peers and (b) negative interactions with teachers and peers to support their subsequent emotion regulation. These findings underscore the role of the preschool classroom as an emotion socialization context for children from low-income households, along with providing additional evidence about the importance of social interactions to understand children's emotional development in context. (PsycInfo Database Record (c) 2022 APA, all rights reserved).