While family functioning interventions show promise for improving adolescent girls’ well-being in humanitarian contexts, few programs employ a gender-transformative approach to maximize benefits for adolescent girls. This paper presents findings from a mixed-methods pilot evaluation of a whole-family, gender-transformative intervention conducted with Syrian refugee families in Jordan. The Siblings Support of Adolescent Girls in Emergencies program was implemented with 60 Syrian refugee households in Azraq and Za’atari camps in Jordan. A quantitative survey was administered to 18 households at baseline and endline, and researchers conducted qualitative interviews and focus group discussions with caregivers, paired interviews and participatory discussions with adolescents, and key informant interviews with program mentors. Paired t-tests revealed statistically significant improvements in mental distress, resilience, and gender equitable attitudes in the full sample and for girls only and marginally significant improvements in family functioning. Qualitative findings revealed improvements in four domains of girls’ well-being—self-efficacy, self-confidence, pro-social behavior, and mental health—through three primary pathways: family members’ increased gender equitable attitudes, healthier intrahousehold communication, and greater affective involvement. Findings from this mixed-methods evaluation point to the potential value in merging gender-transformative and whole-family approaches in humanitarian programming to maximize positive impacts for adolescent girls.