<p class="abstract"><strong>Background:</strong> Approximately 250 million (43%) children under five years in low- and middle-income countries are at risk of sub-optimal development. Of these, 67% are found in sub-Saharan Africa due to exposure to multiple risks, including inadequate stimulation at home. In order to promote early childhood development (ECD), an intervention integrating ECD content into routine facility-based health services and supporting ECD policy and advocacy is currently being implemented in Siaya County. In addition, parental counseling on early stimulation is integrated into home-based visits by community health volunteers. We aim to evaluate the intervention’s operational feasibility, effectiveness and cost-effectiveness.</p><p class="abstract"><strong>Methods:</strong> The study is a cluster-randomized controlled trial using a mixed-methods approach. The study is being conducted in Bondo sub-county in Siaya County. The study has three arms. Arm 1 will receive a health facility-based ECD intervention. Arm 2 will receive the health facility-based ECD intervention combined with home-based ECD counselling. Arm 3 (control) will receive standard care. Six health facilities in each study arm (18 in total) will be randomly selected from wards within the sub-county. We aim to recruit and follow-up 699 mother/caregiver-child dyads, 233 in each arm. Pregnant women are recruited when they visit health facilities during the third trimester. Analysis will involve estimating the effect of the intervention using mixed linear models and the Difference-in-Differences estimator.</p><p class="abstract"><strong>Conclusions: </strong>The data generated from this study will provide much-needed information for program design and implementation of interventions aimed at promoting ECD in Kenya and other sub-Saharan African countries.</p><p class="abstract"><strong>Trial Registration:</strong> Current Control Trial is ISRCTN11561283.</p><p> </p>