Purpose: In social marketing practice, there is no all-encompassing approach that guides researchers and practitioners to build theory-driven social marketing interventions. While the Co-create–Build–Engage (CBE) process offers a roadmap for marketing application, including outlining when and where social marketing’s eight benchmark principles have been applied, limited practical guidance on how and when theory should be applied is offered. This paper reports one case study demonstrating how theory was applied to deliver a theory-informed well-being behavior change intervention. Design/methodology/approach: This paper proposes and applies a new five-step theory-driven social marketing intervention build process (BUILD) drawn from an extensive base of social marketing research and application. Using a case study method, we showcase how the five-step process was applied to inform the design, build and implementation of a well-being behavior change intervention. Findings: This study proposes a five-step process to build theory-driven social marketing interventions called BUILD: Begin with the objective, Use theory, Initiate program design, Let’s produce and Develop the engagement plan. This study provides a step-by-step and easy-to-follow BUILD process which outlines how social marketers can apply a selected theory to inform program design and implementation. Practical implications: The BUILD process offers a roadmap to build theory-driven social marketing interventions that include all elements of intervention development, namely, objective-setting, theory evaluation, selection and application, producing the program and planning for program engagement. Originality/value: This study provides a novel five-step process to help social marketing researchers and practitioners build theory-driven social marketing interventions.