BackgroundPoor early childhood development (ECD) is a major global health concern that is associated with various adverse outcomes over the lifecourse. Parenting interventions especially during the earliest years of life can benefit ECD. However, there is limited evidence from Kenya about the effectiveness of parenting interventions for improving ECD outcomes especially across rural disadvantaged communities. This paper describes the study protocol for an impact and implementation evaluation of a community-based group parenting program that aims to improve ECD in rural Kenya.MethodsWe will conduct a cluster-randomized controlled trial to determine the effectiveness of a parenting program for caregivers of young children in Homabay and Busia counties in Western Kenya. Sixty-four village clusters will be randomly assigned to either the parenting intervention arm or the waitlist control arm with stratification by county. In each village, 10 primary caregivers with a child aged 0–24 months will be enrolled. The parenting program will be delivered through existing peer groups within communities whereby caregivers will receive counseling and psychosocial support to enhance their parenting skills and wellbeing to in turn promote ECD. The intervention curriculum comprises 21 sessions targeting various nurturing care messages, including early learning, responsive caregiving, child nutrition, health, protection, and caregiver mental health. Group sessions are facilitated by a trained volunteer biweekly for a total of 11 months. The primary trial outcome is an overall measure of ECD using the Global Scales of Early Development long form version. Secondary outcomes include various caregiver outcomes (e.g., parenting practices, mental health) and other child outcomes (e.g., socioemotional development, dietary diversity). All outcomes will be assessed at baseline and endline. We will also conduct a qualitative implementation evaluation at endline and interview various stakeholders to assess program fidelity, quality, and sustainability.DiscussionThis trial will evaluate the effectiveness of a parenting intervention on ECD and caregiving outcomes and assess program implementation quality as delivered through existing community-based peer groups. This study will provide rigorous evidence that can be used to inform scale-up of this program model that leverages existing community social networks and resources for improving caregivers’ parenting skills and promoting ECD in rural Kenya and other similar settings across LMICs.Trial registrationClinicalTrials.gov #NCT06165315. Registered on December 11, 2023.