Early school engagement patterns set the stage for short- and long-term academic behaviors and progress, and low engagement at school entry can give rise to dysfunctional school behavior and underachievement in later years. Relationships with parents and teachers provide a foundation upon which children develop the skills and behaviors that are critical for engagement in early elementary school. However, the cross-contextual and transactional processes by which these relationships are associated with engagement in early elementary school remain unclear. This investigation therefore considers how children’s relationships with parents prior to school entry are indirectly and interactively associated with 1st grade engagement through teacher–child relationships. It also considers how early cognitive, self-regulatory, and behavioral skills and competencies elicit these relational responses. This investigation drew upon multimethod data from triangulated sources (parents, teachers, and direct observation) available within a large longitudinal study, the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development. Results indicate that neither 54-month or 1st grade parent–child relationships were directly associated with children’s engagement in early elementary school. However, 1st grade teacher conflict was problematic for children’s developing engagement. In turn, teacher conflict partially mediated linkages between maternal sensitivity and conflict prior to school entry and engagement in 1st grade. Parental closeness and sensitivity also buffered children against negative associations between teacher conflict and engagement. Finally, children’s early skills and competencies at 36 months elicited relational processes that were indirectly associated with engagement. Conceptual, theoretical, and methodological challenges are also discussed.