It has been well-established that development occurs in the context of a transactional framework, with bidirectional parent-child interactions influencing both proximal and distal outcomes. In particular, child vocabulary development is sensitive to parenting qualities including warmth, sensitivity, and control as well as parental stimulation including language input and access to learning enrichment activities. Similarly, these parenting qualities are influenced by and influence children's development of pro-social behaviors. Given the foundational role of both language and pro-social skills for academic achievement and the establishment of healthy relationships across the lifespan, a comprehensive understanding of the magnitude, stability, and reciprocity of such interactions across childhood has the potential to better inform early intervention and prevention practices and highlight risk and resilience factors. This study investigated the concurrent and successive transactional relationships between child pro-social behavior, child emergent language, and parenting qualities within a large, longitudinal sample. This study utilized Waves 3, 4, and 5 of the Fragile Families and Child Well Being Study (FFCWBS), corresponding to focal child age 3, 5, and 9 years, respectively. A series of Structural Equation Modeling (SEM) with full-information likelihood (FIML) estimation (n = 3,422) including child prosocial behavior, receptive vocabulary, and supportive parenting behaviors was tested and compared. Our findings indicate significant, positive associations over time between child pro-social behavior and receptive vocabulary, and parenting quality across all three stages of early child development. The steady decline in magnitude of these associations over time highlights the importance of synergistic parent-child interactions in toddlerhood as an early opportunity to propel these developmental outcomes and supportive parenting behaviors. Patterns of change in child pro-social behavior skills and parenting qualities remained positive and relatively stable, while observed growth in child receptive vocabulary skills increased in magnitude over time. Additional investigation of indirect effects specified the role of receptive vocabulary, as well as the bolstering role of prosocial behavior, in eliciting responsive parenting qualities over time.