For children with low self-regulation in the preschool years, the likelihood of poorer intellectual, health, wealth and anti-social outcomes in adulthood is overwhelming. Yet this knowledge has not yielded a framework for understanding self-regulatory change, nor generated particularly successful methods for enacting this change. Reconciling insights from cross-disciplinary theory, research and practice, this study seeks to implement a newly developed program of low-cost and routine practices and activities for supporting early self-regulatory development within preschool contexts and to evaluate its effect on children's self-regulation, executive function and school readiness; and educator perceived knowledge, attitudes and self-efficacy related to self-regulation.The Early Start to Self-Regulation study is a cluster randomized, controlled trial for evaluating benefits of the Preschool Situational Self-Regulation Toolkit (PRSIST) program, when implemented by early childhood educators, compared with routine practice. The PRSIST program combines professional learning, adult practices, child activities and connections to the home to support children's self-regulation development. Fifty preschool centers in New South Wales, Australia, will be selected to ensure a range of characteristics, namely: National Quality Standards (NQS) ratings, geographic location and socioeconomic status. After collection of baseline child and educator data, participating centers will then be randomly allocated to one of two groups, stratified by NQS rating: (1) an intervention group (25 centers) that will implement the PRSIST program; or (2) a control group (25 centers) that will continue to engage in practice as usual. Primary outcomes at the child level will be two measures of self-regulation: Head-Toes-Knees-Shoulders task and the PRSIST observational assessment. Secondary outcomes at the child level will be adult-reported measures of child self-regulation, executive function and school readiness. Outcomes at the educator level will involve a survey of their perceived knowledge, attitudes and self-efficacy for supporting children's self-regulatory development. In all cases, data collectors will be blinded to group allocation.This is the first randomized controlled trial of a new program to foster early self-regulation, using low-cost practices and activities that are aligned with early-years contexts, routines and practices. Results will provide important information about the efficacy of this approach and evaluate its underlying model of self-regulatory change.Australian New Zealand Clinical Trials Registry, ACTRN12617001568303 . Registered on 21 November 2017.