BACKGROUND: Though family satisfaction with prehospital care is a surrogate for quality and patient outcomes, there are no tools available to measure family satisfaction. OBJECTIVE: To develop the EMS Family Assessment of Medical Interventions & Liaisons with the Young (FAMILY) instrument. METHODS: Components of family experiences with pediatric prehospital care were identified with a modified Delphi method. The expert panel included Emergency Medical Technicians, paramedics, family representatives, and EMS leaders from Colorado, Connecticut, and Rhode Island. An online survey was used to assess proposed questions from each of five candidate domains from national guidelines, including Safety, Communication, Family Presence, Cultural Awareness, Children with Special Healthcare Needs and Overall Satisfaction. Round-1 items were scored on a five-point Likert scale. Inclusion in the final instrument required 70% agreement ranking items as "" or "." In Round-2, participants assessed proposed refinements. This resulted in FAMILY Version-1, with sections for family members and EMS care providers. EMSC Family Action Network (FAN) representatives evaluated the FAMILY, leading to Version-2. Suggestions from the national FAN about content, clarity, and whether the instrument captured their experiences with pediatric EMS care led to the final FAMILY version. Bilingual speakers translated the instrument into Spanish, while assessing the content for semantic, idiomatic, experiential, and conceptual equivalence between the English and Spanish versions. RESULTS: There were 22 experts in Round-1, and 20 continued into Round-2 .The Delphi process yielded 12 questions in six domains with 14 recommended modifications. Two questions were excluded. Five domains reached 70% agreement in Round-1. Cultural Awareness reached 75% agreement after Round-2. Six FAN representatives evaluated Version-1, leading to changes for clarity, content and cultural sensitivity. Seventeen FAN representatives evaluated Version-2 leading to additional refinement. The assessment of the equivalence between the English and Spanish survey versions resulted in changes in the Spanish language content for equivalent meaning. CONCLUSION: A panel of EMS and family stakeholders successfully developed an instrument to assess family satisfaction with pediatric EMS care. Further validation is required in a large respondent population. Assessing family satisfaction with pediatric EMS encounters is an important step toward improving prehospital care.