--- - |2 Abstract Self‐regulation is a dynamic process wherein executive processes (EP) delay, minimize or desist prepotent responses (PR) that arise in situations that threaten well‐being. It is generally assumed that, over the course of early childhood, children expand and more effectively deploy their repertoire of EP‐related strategies to regulate PR. However, longitudinal tests of these assumptions are scarce in part because self‐regulation has been mostly studied as a static construct. This study engages dynamic systems modeling to examine developmental changes in self‐regulation between ages 2 and 5 years. Second‐by‐second time‐series data derived from behavioral observations of 112 children (63 boys) faced with novel laboratory‐based situations designed to elicit wariness, hesitation, and fear were modeled using differential equation models designed to capture age‐related changes in the intrinsic dynamics and bidirectional coupling of PR (fear/wariness) and EP (strategy use). Results revealed that dynamic models allow for the conceptualization and measurement of fear regulation as intrinsic processes as well as direct and indirect coupling between PR and EP. Several patterns of age‐related changes were in line with developmental theory suggesting that PR weakened and was regulated more quickly and efficiently by EP at age 5 than at age 2. However, most findings were in the intrinsic dynamics and moderating influences between PR and EP rather than direct influences. The findings illustrate the precision with which specific aspects of self‐regulation can be articulated using dynamic systems models, and how such models can be used to describe the development of self‐regulation in nuanced and theoretically meaningful ways. - Developmental Science, Volume 21, Issue 5, September 2018.