Families of persons with acquired brain injuries need to be supported from the early phase of hospitalization. To date, no known early family intervention is available for this population. Using the Medical Research Council Framework, we developed a new intervention based on the Calgary Assessment and Intervention Models that includes the family preferences, clinician’s expertise, and the contextual resources. This paper aims to describe the complete development process including a scoping review, an assessment of families and clinicians’ needs, an evaluation of the contextual resources, and an adaptation of the theoretical framework. Using a systemic perspective, we tailored the new intervention to involve the stakeholder’s preferences. The result is an early family intervention named SAFIR©, led by a clinical nurse specialist, including five core components and structured around three phases and a follow-up. The next steps will be focused on assessment of the clinical feasibility of this new intervention.