Background <p>Behavioral interventions are well-established treatments for emerging externalizing problems in preschool. However, caregivers and teachers face barriers to implementing behavioral interventions across home and school. The current study aims to improve joint teacher and caregiver uptake and adherence to a behavioral intervention by testing a new adjunctive intervention co-developed with early childhood constituents, Parent-Educator Action Response (PEAR). PEAR consists of group-based motivational interviewing, psychoeducation, and action planning sessions for preschool teachers and caregivers of a preschooler with elevated externalizing problems, followed by a meeting with each caregiver-teacher dyad to agree upon a plan for supporting improvements in the child’s externalizing problems.</p> Methods <p>We will use a pilot Roll-Out Implementation Optimization (ROIO) design, with three clusters over 18&#xa0;months to implement and evaluate PEAR. Participants will be approximately 24 preschool teachers and 24 caregivers of a preschool child. All participants will receive PEAR, delivered by a licensed clinical psychologist and supported by a bilingual community health worker. Throughout the study period, participants will be asked to implement the Daily Report Card (DRC), an evidence-based behavioral intervention for externalizing problems. Implementation of the DRC at home and preschool, the primary outcome, will be measured weekly for eight weeks. Additional outcomes will be measured at baseline, post-PEAR, and follow-up (4&#xa0;weeks post-PEAR).</p> Discussion <p>This is one of the first pilot ROIO trials and trials in the preschool setting to study a new adjunctive intervention to improve both teacher and caregiver uptake and adherence to behavioral interventions for preschool externalizing problems. Findings are likely to generalize to other public health adjunctive interventions in community settings.</p> Trial registration <p>clinicaltrials.gov NCT 07203014 on 10–02-2025.</p>