BACKGROUND: Despite the increasing evidence on the importance of contextual adaptation of interventions, there is limited understanding of how intervention adaptations made for one context can inform adaptation and implementation efforts in others or how to harmonize adapted interventions for use across multiple contexts. PURPOSE: This paper outlines the process used to further adapt and harmonize previous Kenyan and Ethiopian cultural and contextual adaptations of the World Health Organization's Caregiver Skills Training intervention as a case study to propose a framework for similar efforts. It also outlines key lessons learned. RESULTS: The Compare, Decide, Develop drafts, and Test and train (CoDDaT) framework is a four-phased, stepwise approach to intervention adaptation and harmonization that involves: (i) comparing available intervention materials and measures across contexts, (ii) deciding in collaboration with key stakeholders on adaptations needed, (iii) developing drafts of harmonized intervention materials and measures, and (iv) testing harmonized intervention materials and measures and training staff. It complements existing implementation frameworks by describing the preparatory phase ahead of implementing an adapted or harmonized project. Critical lessons learned included the importance of accurate documentation, the team's phase-specific size and composition, time management, and the opportunities for network growth and skills development offered by the harmonization process. CONCLUSIONS: We demonstrate how lessons from context-specific adaptations can be applied cross-culturally, while incorporating critical revisions and preserving core intervention components. CoDDaT may inform efforts to adapt and implement interventions to promote health behavior change across contexts and advance the field by challenging interventionists to move beyond single-context-focused adaptations and consider applying adapted interventions to other similar contexts, harmonizing, or refining adapted interventions for more extensive use.