Given the robust evidence-base for the efficacy of cognitive behavioral therapies (CBTs) in reducing youth anxiety disorders, researchers have moved beyond efficacy outcome analysis to better understand how such interventions operate (i.e., mediation). However, the majority of this research has examined mechanisms of change in CBTs targeting anxiety in school-age youth or adolescents, and applying such findings to younger children may be misguided. Grounded in developmental-transactional models, interventions for younger children with or at risk for anxiety tend to target key parenting and child factors implicated in the early emergence and maintenance of anxiety. Nevertheless, the directional and temporal relations among these child and parenting factors in the context of early interventions remain unknown. The current study thus builds on previous studies of CBT for older youth to elucidate mechanisms of change and treatment directionality within two early interventions for young children (N = 151) at risk for anxiety by virtue of behavioral inhibition: The multi-component Turtle Program and the parent-only Cool Little Kids program. Reciprocal relations between parent-reported child anxiety, observed parenting (negative control and positive affect), and parent-reported accommodation of child anxiety were examined across 4 timepoints (pre-, mid-, and post-treatment, and one-year follow-up). Study hypotheses were tested via 1) a traditional cross-lagged panel model (CLPM), 2) a latent curve model with structured residuals (LCM-SR), and 3) a latent change score model (LCS). Results were consistent with the child-to-parent influences found in previous research on CBT for older anxious youth. However, after extending the traditional CLPM to parse within- and between-person effects in the LCM-SR, these results only remained in Turtle. LCS analyses revealed bidirectional effects of changes in parent accommodation and changes in child anxiety during and after the intervention, but only in Turtle. Our findings coincide with developmental-transactional models suggesting that the development of child anxiety may be the result of child-to-parent influences rather than just the reverse, and highlight the importance of targeting parent and child factors simultaneously in early interventions for young inhibited children and their parents.