Protective parenting, when enacted in contexts that do not require it, predicts child anxiety. Both child (e.g., temperament) and maternal (e.g., physiology and cognition) factors relate to parenting behavior, supporting family systems theory. In order to better understand the development of environmental risk for child anxiety, the present study applied the integrated social information and emotion processing theory to protective parenting, assessing concurrent relations among child temperament, maternal physiology, maternal cognitions, and protective parenting in toddlerhood. The present study also investigated whether the theory could be applied to longitudinal relations, testing cognition as a mechanism by which maternal physiology and child temperament predict maternal protective parenting over time. Study participants included 189 mothers (89.9% White, 2.1% Hispanic, 32.3% with annual household income ≤$40,000) and children (55.6% male, 81.0% White, 3.7% Hispanic). Results indicated that the theory was partially applicable to both concurrent and prospective mother–child relations implicated in child anxiety development. Namely, child inhibited temperament (IT) related concurrently to maternal beliefs about the harm of child anxiety at child age 1 year, and to maternal protective parenting at child ages 2 and 3 years. Maternal baseline respiratory sinus arrythmia related to protective parenting at child age 3 years. Longitudinally, maternal beliefs at child age 1 year predicted maternal perceptions of child IT at child age 2 years. Maternal beliefs at child age 2 years predicted maternal protective parenting at child age 3 years. Although the mechanistic role of cognition was not supported, child emotion processes and maternal cognitions may uniquely contribute to maternal protective parenting. [ABSTRACT FROM AUTHOR]