Research Findings: Preschoolers' vocabulary skills and inhibitory control have been demonstrated critical for later school success; however, the ways in which the individual classroom experiences dynamically interchange with these skills is still unclear. In this paper, we examine the role of children's individual engagement with teachers, peers, and tasks in facilitating children's skill development across the school year. Using a sample of 895 preschoolers across 223 classrooms drawn from the Professional Development Study, the current study examined engagement as both outcomes of children's vocabulary and inhibitory control in the fall of the preschool year and as mediators of linkages between them across the preschool year. Results suggested that vocabulary skills and inhibitory control each shape different aspects of classroom engagement. Children's vocabulary was associated with positive engagement with teachers and peers, whereas inhibitory control was associated with positive task engagement and negative engagement. We also found that negative engagement as composited by conflicts with teachers and peers and off-task behaviors mediated the association between fall inhibitory control with spring vocabulary and inhibitory control. Practice or Policy: Together, these findings suggest the critical role of individual classroom experiences in explaining children's vocabulary and inhibitory control development.